Problem: I can use this background: Predators play an important role in an ecosystem. For example, if they did not exist, then a single species could become dominant over others. Grazers on a grassland keep grass from growing out of control. Predators can be keystone species . These are species that can have a large effect on the balance of organisms in an ecosystem. For example, if all of the wolves are removed from a population, then the population of deer or rabbits may increase. If there are too many deer, then they may decrease the amount of plants or grasses in the ecosystem. Decreased levels of producers may then have a detrimental effect on the whole ecosystem. In this example, the wolves would be a keystone species. Now, I have a new situation: Dan and Joe studied animals for biology class. Joe had to study predator animals, while Dan studied herbivores and grazers. Answer this question please: Which student learned less about the balance of organisms in an ecosystem?

A: Joe

Problem: I can use this background: As Figure above shows, the distance between particles is much smaller for the solid and liquid states than for the gas state. In the solid state, particles are fixed in place, while particles are more free to move in the liquid and gas states. The particles in the solid and liquid states "stick together," but in the gas state, they move freely about the container. In general, it requires energy to separate individual particles. If we want to make a solid adopt a liquid form, we can add energy in the form of heat, increasing the temperature of the substance. Conversely, if we want to convert a substance from a gas to a liquid or from a liquid to a solid, we remove energy from the system and decrease the temperature. Pressure also plays an important role in changes of state, which will be discussed later on. We will study these difference in greater detail in the chapter States of Matter. Now, I have a new situation: John is studying the different states of matter. Today, he has a matter in three states in front of him, state A, state B, and state C. State A is in solid state. State B is in liquid state. And, state C is in gaseous state. He needs to determine the properties of each state. Answer this question please: In which state the particles are less free, state A or state B?

A: state A

Problem: I can use this background: Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of the glacier. Air bubbles are squeezed out and ice crystals enlarge, making the ice appear blue. Small amounts of regular ice appear to be white because of air bubbles inside them and also because small quantities of water appear to be colourless. In glaciers, the pressure causes the air bubbles to be squeezed out, increasing the density of the created ice. Large quantities of water appear to be blue, as it absorbs other colours more efficiently than blue. A large piece of compressed ice, or a glacier, similarly appears blue. Now, I have a new situation: Mike likes to visit places. This winter he is visiting Greenland. First, he visited Lake A, which is very small. Then he visited Lake B, which is huge. While visiting Lake B he went to a local pub. There he heard other tourists talking about two nearby glaciers, glacier C and glacier D. They said that glacier C had a snowfall and the snow became part of the glacier, but glacier D didn't have any snowfall. Mike is getting ready to visit those glaciers. Answer this question please: If Mike wants to see blue ice, which glacier should he visit?

A: glacier C

Problem: I can use this background: Iron is first oxidized to iron(II) ions by oxygen. In the second step, the iron(II) ions are further oxidized and combine with water and oxygen gas to produce a hydrated form of iron(III) oxide known as rust. Rusting is one of many example of corrosion. Corrosion is the deterioration of metals by redox processes. Corrosion causes enormous amounts of damage to buildings, bridges, ships, cars, and other objects. It has been estimated that corrosion costs the U.S. economy over 100 billion dollars each year. A great amount of time and effort is spent to try to limit or prevent corrosion. Now, I have a new situation: Two neighboring cities had different climates. Dune city had very dry air and no rain, while Bay city had very high humidity, fog and lots of rain. Answer this question please: Which city had more damage to buildings because of corrosion?

A:
Bay