Question

the movement of ocean currents can also form deserts. when moist air masses travel east over an ocean, they drop most of their moisture as precipitation. by the time the air reaches the west coast of a continent, it is very dry. one mid - current desert is the atacama in chile, south america.
some deserts, like the gobi in central asia, form because a mountain range blocks them from getting rain. others, like the great australian desert, form in the center of a continent because they are far from moisture - rich ocean winds.
based on the passage, which of these is the most likely explanation for why deserts form?
choose one option
a the air over deserts has already dropped its moisture somewhere else, so it ends up very dry.
b deserts get 30 percent more sunlight than other areas of the earth, and that is why they are so hot.
c the sahara was the first desert on earth, and other deserts formed around it as time went by.
d ocean currents cause precipitation to fall steadily, but desert sand absorbs the moisture too quickly.

Explanation:

The passage mentions that when moist air masses travel east over an ocean, they drop most of their moisture as precipitation. By the time the air reaches the west coast of a continent, it is very dry. This supports option A. Option B is not mentioned in the passage. Option C is incorrect as there is no indication that the Sahara was the first desert. Option D is also not supported by the text.

Answer:

A. The air over deserts has already dropped its moisture somewhere else, so it ends up very dry.