As food is pushed along, it undergoes digestion. Digestion is the process of breaking down food into nutrients. There are two types of digestion: mechanical digestion and chemical digestion. Mechanical digestion occurs when large chunks are turned into smaller chucks. Perhaps not surprisingly, this happens when you chew your food. Once you swallow the food, your stomach also does some of this work. Chemical digestion occurs when food is broken down into useful nutrients. This is a chemical process that begins as you start to chew your food. The saliva in your mouth starts this process. Once you swallow, the acid in your stomach further breaks down food. From the stomach, the foods moves into the small intestine. In the small intestines, another set of chemicals goes to work. Are you surprised? Your small intestine, and not your stomach, does most of the work!

Question: "What does mechanical digestion involve?"

OPTIONS:
- no
- yes

Answer: "When food is broken down into useful nutrients"

Response: no

Fossils give clues about major geological events. Fossils can also give clues about past climates. Fossils of ocean animals on the top of a mountain? Ocean animals have been found on the Earths tallest mountain. Its hard to believe, but it is true. These fossils were found at the top of Mt. Everest. Mt. Everest is the highest mountain on Earth. These fossils showed that this entire area was once at the bottom of a sea. It can only mean that Mt. Everest was uplifted. In fact, the entire Himalaya mountain range was raised. It was forced up from the collision of two continents. Fossils of plants are found in Antarctica. Now, Antarctica is almost completely covered with ice. Plants do not grow in Antarctica. According to fossils, they once did. This means that Antarctica was once much warmer than it is now. These fossils tell us about Antarcticas past climate.

Question: "What Is the evidence that temperature used to be warmer in Antarctica?"

Response: "People who lived there a long time ago left notes saying it was warm"
OPTIONS:
- no
- yes

A: no

Problem: So what is gravity? A typical definition of gravity is that it is a force. It causes an attraction between two masses. According to this definition, anything that has mass exerts a force. Any object exerts gravity on other objects. It does not matter how small it is, it has gravity. The more matter an object has, the more gravity it has. Your pencil has a tiny bit of gravity, but far too little to notice. What about a planet? It would have a lot of gravity. An objects gravity exerts a pull on other objects. Friction only occurs between objects that are touching. Gravity can act between objects that are not touching. In fact, gravity can act over very long distances. Where else can you feel gravity?

Question: "How do objects interact under gravity?"

Answer: "there is friction"

OPTIONS:
- no
- yes
Answer: no

Question:
Chemical changes produce new substances. For this reason, they often cannot be undone. Some chemical changes can be reversed, sort of. To do so requires another chemical change to take place. For example, you can undo the tarnish on copper pennies by placing them in vinegar. The acid in the vinegar reacts with the tarnish. This is a chemical change that makes the pennies bright and shiny again. You can try this yourself at home to see how well it works. Other chemical changes cannot be reversed at all or may be difficult to do. Rusting is a chemical change. If metal rusts, the best you can do is to sand off the rust to get down to the shiny metal. Although the metal may now be shiny, the rust was removed. The rust was not changed back into the original metal. Some chemical reactions occur in only one direction. These reactions are called irreversible reactions. For example, you cannot change a fried egg back into a raw egg. Can you think of some other irreversible reactions related to cooking? Would you like a piece of cake? After reading the above, is "placing pennies in vinegar" the correct answer to the question "What can you do to make pennies bright and shiny again?"? OPTIONS:
- no
- yes

Answer:
yes

Hundreds of thousands of years before China was to become the world's longest-running civilization, the prologue was enacted by means of the flicker of a carefully tended fire. Peking Man, a forebear of Homo sapiens, achieved a mastery of fire. We might call it the first Chinese invention. Not that he devised flint and steel, matches, or any other way of creating fire. Peking Man simply learned how to capture flame, perhaps from a forest fire, and keep it alight. He thus enjoyed two revolutionary luxuries: light and heat. Technologically and sociologically, it was a phenomenal breakthrough: with fire, communities could live year 'round in one cave, in which cooking and even smelting could be pursued. And so, by 600,000 b.c., about 50 km (31 miles) southwest of present-day Beijing, the ancestors of mankind were ready to settle down. Several hundred thousand years later, when Marco Polo reached the capital of China, he was astonished by a further development in fire technology. The Chinese, he announced, used black stones dug out of mountains as fuel. Europeans did not yet have a word for "coal," nor had they discovered a use for it. The First Dynasty The confluence of mythology and history in China took place around 4,000 years ago during what is referred to as the Xia (Hsia) Dynasty. This was still the Stone Age, but the people are thought to have made silk from thread produced by the worms they cultivated on the leaves of their mulberry trees. And written language (which evolved as early as 4,500 to 5,000 years ago) was already in use, originally by oracles and then by official scribesChina's first scholars. During the second of the quasi-legendary dynasties, the Shang (from about the 16th to 11th centuries b.c.), the Chinese developed an interest in art. Careful geometric designs as well as dragon and bird motifs adorned bowls and implements. And with the arrival of the Bronze Age, the Chinese created bronze vessels of such beauty and originality that, until modern times, archaeologists refused to believe they were cast 3,000 years ago. The Shang Dynasty gave rise to the concept of one Chinese nation under one government.

Question: "What were the Chinese using coal for?"

OPTIONS:
- no
- yes

Answer: "Fuel"

Response:
yes