instruction:
Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
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Context: Weathering changes solid rock into sediments. Sediments are different sizes of rock particles. Boulders are sedi- ments; so is gravel. At the other end, silt and clay are also sediments. Weathering causes rocks at the Earths surface to change form. The new minerals that form are stable at the Earths surface. It takes a long time for a rock or mountain to weather. But a road can do so much more quickly. If you live in a part of the world that has cold winters, you may only have to wait one year to see a new road start to weather (Figure Mechanical weathering breaks rock into smaller pieces. These smaller pieces are just like the bigger rock; they are just smaller! The rock has broken without changing its composition. The smaller pieces have the same minerals in the same proportions. You could use the expression a chip off the old block to describe mechanical weathering! The main agents of mechanical weathering are water, ice, and wind. Rocks can break apart into smaller pieces in many ways. Ice wedging is common where water goes above and below its freezing point (Figure 9.2). This can happen in winter in the mid-latitudes or in colder climates in summer. Ice wedging is common in mountainous regions. This is how ice wedging works. When liquid water changes into solid ice, it increases in volume. You see this when you fill an ice cube tray with water and put it in the freezer. The ice cubes go to a higher level in the tray than the water. You also may have seen this if you put a can of soda into the freezer so that it cools down quickly. If you leave the can in the freezer too long, the liquid expands so much that it bends or pops the can. (For the record, water is very unusual. Most substances get smaller when they change from a liquid to a solid.) Abrasion is another type of mechanical weathering. With abrasion, one rock bumps against another rock. Gravity causes abrasion as a rock tumbles down a slope. Moving water causes abrasion it moves rocks so that they bump against one another (Figure 9.3). Strong winds cause abrasion by blasting sand against rock surfaces. Finally, the ice in glaciers cause abrasion. Pieces of rock embedded in ice at the bottom of a glacier scrape against the rock below. If you have ever collected beach glass or pebbles from a stream, you have witnessed the work of abrasion. Sometimes biological elements cause mechanical weathering. This can happen slowly. A plants roots grow into a crack in rock. As the roots grow larger, they wedge open the crack. Burrowing animals can also cause weathering. By digging for food or creating a hole to live in the animal may break apart rock. Today, human beings do a lot of mechanical weathering whenever we dig or blast into rock. This is common when we build homes, roads, and subways, or quarry stone for construction or other uses. Mechanical weathering increases the rate of chemical weathering. As rock breaks into smaller pieces, the surface area of the pieces increases. With more surfaces exposed, there are more places for chemical weathering to occur. Lets say you wanted to make some hot chocolate on a cold day. It would be hard to get a big chunk of chocolate to dissolve in your milk or hot water. Maybe you could make hot chocolate from some smaller pieces like chocolate chips, but it is much easier to add a powder to your milk. This is because the smaller the pieces are, the more surface area they have. Smaller pieces dissolve more easily. Chemical weathering is different than mechanical weathering. The minerals in the rock change. The rock changes composition and becomes a different type of rock. Most minerals form at high pressure or high temperatures deep within Earth. But at Earths surface, temperatures and pressures are much lower. Minerals that were stable deeper in the crust are not stable at the surface. Thats why chemical weathering happens. Minerals that formed at higher temperature and pressure change into minerals that are stable at the surface. Chemical weathering is important. It 
 Question: weathering process that occurs when rocks and rock particles scrape other rocks
answer:
abrasion


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Context: The following are selected contributors' notes for an essay collection. KATY BUTLER, a 2004 finalist for a National Magazine Award, has written for The New Yorker, the New York Times, Mother Jones, Salon, Tricycle, and other magazines. She was born in South Africa and raised in England, and came to the United States with her family at the age of eight. "Everything Is Holy," her essay about nature worship, Buddhism , and ecology, was selected for Best Buddhist Writing 2006. In 2009 she won a literary award from the Elizabeth George Foundation. "What Broke My Father's Heart" was named a "notable narrative" by the Nieman Foundation for Journalism at Harvard, won a first-place award from the Association of Health Care Journalists, and was named one of the 100 Best Magazine Articles of All Time. Butler has taught narrative nonfiction at Nieman Foundation conferences and memoir writing at Esalen Institute. Her current book project is Knocking on Heaven's Door: A Journey Through Old Age and New Medicine to be published in 2013. VICTOR LAVALLE is the author of a collection of stories, Slapboxing with Jesus, and two novels, The Ecstatic and Big Machine, for which he won the Shirley Jackson Award, the American Book Award, and the Ernest J. Gaines Award for Literary Excellence. He is a 2010 Guggenheim Award winner and an assistant professor at Columbia University's School of the Arts. About "Long Distance" he says: "This essay actually came about when I was asked to write about my life after having lost a great deal of weight. And yet, when I sat down to work, all I could do was return to that time when I was much heavier and deeply unhappy. Why? I sure didn't miss those days. And yet, I felt I couldn't write about my present without touching on that past. But, of course, I never reach the true present in the essay. Maybe I still don't know how to talk about a life with greater happiness. " BRIDGET POTTER was born in Brompton-on-Swale, Yorkshire, and came to the United States as a teenager in 1958. She spent the first forty years of her career in television, beginning as a secretary, then as a producer and an executive, including fifteen years as senior vice president of original programming at HBO. In 2007 she earned a BA in cultural anthropology from Columbia University. This year she will complete an MFA in nonfiction, also from Columbia, where she has been an instructor in the University Writing Program. She is currently working on her first book, a memoir / social history of the 1960s, from which her essay "Lucky Girl" is adapted. PATRICIA SMITH is the author of five books of poetry, including Blood Dazzler, chronicling the tragedy of Hurricane Katrina, which was a finalist for the 2008 National Book Award, and Teahouse of the Almighty, a National Poetry Series selection. Her work has appeared in Poetry, The Paris Review, TriQuarterly, and The Best American Poetry 2011. She is a Pushcart Prize winner and a four-time individual champion of the National Poetry Slam, the most successful poet in the competition's history. RESHMA MEMON YAQUB wouldn't even be fit to write a grocery list were it not for her guardian editors. Her stories owe many glorious plot twists to Zain, eleven, and Zach, seven. Ditto their dad (Amer) and grandparents (Ali, Razia, Muhammad, Nasreen). Costars: Sophie, Sana, Yousef, and Maryam. Miss Yaqub lives in Bethesda, Maryland. Her next project is an investigation into the whereabouts of two missing people: Mr. Right and Ms. Memoir Literary Agent. 
 Question: Who is the most successful poet in the competition's history?
answer:
patricia smith.


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Context: New research shows how kids' brains reorganize as they learn math. All the time you spent memorizing multiplication tables may have made you a better mathematician, according to a new study. A team of scientists from Stanford University, in California, have shown how the brain reorganizes itself as kids learn math. After a certain amount of time spent practicing math, kids can put away the calculator . They don't even need to count on their fingers. They simply know the answers to subtraction , addition, and multiplication facts. The quicker kids can recall basic math facts, the easier it is for them to solve more complicated math problems. The Stanford University researchers observed the brain activity of 28 students aged 7to 9 for the study. They took scans of the students' brains as the students solved math calculations without the help of a calculator, pen or paper. A calculation--three plus four equals seven, for example--flashed on a screen. The students pushed a button to say if the answer was right or wrong. The scientists also recorded the response speed, and what parts of the brain became active as the kids pushed the button. These observations showed a process called fact retrieval . Rather than using their fingers to count, or writing out answers on a piece of paper, the students pulled the answers from memory. It's as if the answers to basic math problems are kept in a long-term storage area in the brain, which was built from repetition. "Experience really does matter," said Dr. Kathy Mann Koepeke. Children make the shift from counting to fact retrieval when they are 8 to 9 years old, the study shows. This is the time when most students are learning basic addition and subtraction. When kids have basic math facts memorized, the brain has more free space to learn more complicated math. This process has benefits for the future. The study shows as kids grow older, their answers rely more on memory and become quicker and more accurate. Less brain activity is devoted to counting. Some children make this shift quicker than others. 
 Question: What plays a key role in solving a math problem?
answer:

experience