Why does the angle at which the Sun’s rays hit the Earth change during the year, and how does this cause the seasons to differ in temperature and day length?

Explanation:

This is due to the tilted earth's axis. During the summer, the sun's beams hit the Earth at a steep angle. The light does not spread out so a lot, subsequently expanding the measure of energy hitting any given spot. Likewise, the long daylight hours permit the Earth plenty of time to reach warm temperatures.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.