Read the following article and select the best answer. Article: 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... Question: What happens to kids when they are 8 to 9 years old? - Their brains are more active than before. - They depend on fact retrieval for answers. - They become more interested in learning math. - They work out complicated problems more quickly.
They depend on fact retrieval for answers.

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Read the following article and select the best answer. Article: Everyone has those nights-you lie in your bed for hours, tossing and turning, totally unable to fall asleep. You wish you could just turn your brain off as if it were a light. That would make things much easier, wouldn't it? Now it looks like you are one step closer to this wild dream of yours-scientists from Oxford University, UK have just discovered the "switch" that tells the brain to go to sleep, reported Forbes. To understand the study, you first need to know that there are two mechanisms that regulate sleep. There's one that we're already familiar with --our body clock, which works in a 24-hour cycle based on the light changes throughout the day. The other one is what scientists call the sleep "homeostat ". This mechanism has nothing to do with daylight. Instead, it keeps track of the brain's waking hours and urges it to rest if it has been awake for a long time. "It is similar to the thermostat in your home. A thermostat measures temperature and switches on the heating if it's too cold," Professor Gero Miesenbock, who led the study, told The Telegraph. Our bodies use both of the mechanisms to regulate sleep. "The body clock says it's the right time, and the sleep thermostat has built up pressure during a long waking day," explained Miesenbock. There is no way that scientists can trick the body clock. But with the sleep homeostat, there might be something they can do. The researchers found that the sleep homeostat works by activating a specific group of nerve cells, or neurons, in the brain. They tested their theory on fruit flies by removing the neurons from the insects' brains. And as expected, they found that the flies without the homeostat neurons did not keep a regular sleep pattern anymore. Now that scientists have pinpointed the exact place in the brain-- or, the "switch"--that regulates sleep, they can begin investigating how to activate these cells at any given time so that people can be sent to sleep instantly. More importantly, figuring out how sleep mechanisms work may also help us to one... Question: How does the author explain the function of the sleep homeostat? - Through examples. - With comparisons. - Through cause and effect analysis. - By presenting research findings.
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With comparisons.

Question: Read the following article and select the best answer. Article: Each time I see a balloon , my mind flies back to a memory when I was a six-year-old girl . It was a rainy Sunday and my father had recently died . I asked my mum if my dad had gone to heaven . " Yes , honey . Of course , " she said . " Can we write him a letter ? " She paused , the longest pause of my short life , and answered , " Yes . " My heart jumped . " Can the mailman go there ? " I asked . " No , but I have an idea . " Mum drove to a party store and returned with a red balloon . I asked her what it was for . " Just wait , honey . You'll see . " Mum told me to write my letter . Eagerly , I got my favorite pen , and poured out my six-year-old heart in the form of blue ink . I wrote about my day , what I learned at school , how Mum was doing , and even about what happened in a story I had read . For a few minutes it was as if Dad were still alive . I gave the letter to Mum . She read it over , and a smile crossed her face . She made a hole in the corner of the letter to tie it to the balloon . We went outside and she gave me the balloon . It was still raining . " Okay , on the count of three , let it go . One , two , three . " The balloon , carrying my letter , flew upwards against the rain . We watched until it was swallowed by the mass of clouds . Later I realized , like the balloon , that Dad had never let his sickness get him down . He was strong . No matter what he suffered , he'd keep on , fly up , and finally go beyond this cold world and his sick body . He rose into sky and became something beautiful . I watched until the balloon disappeared into the grey and white and I prayed that his strength was passed on . I prayed to be a balloon . Question: In the eyes of the author , what was the rain like ? - An incurable disease . - Her unforgettable memory . - The pain her mother suffered . - The hard time her father had .
Answer:
The hard time her father had .