Question

in the water cycle, water travels around the planet in a repeating set of steps. water from the surface of the earth goes into the air. for example, when the ocean is heated by the sun, some of the water evaporates. in other words, it turns into water vapor, a gas. the water vapor then rises into the sky. when water vapor starts to condense, or change to liquid water, clouds form. next, when the clouds are full of water, tiny drops form. the drops fall to earth as rain or snow. over time, the water will evaporate again, continuing the cycle.
what is the main, or central, idea of the passage?
water moves around the earth in a series of steps known as the water cycle.
when the suns rays heat the oceans water, the water turns into water vapor.
the water cycle takes place all around us all the time.

Explanation:

The passage starts by stating that in the water cycle, water travels around the planet in a repeating set of steps. Then it details each step (evaporation, condensation, precipitation, and then evaporation again). The other two options are just parts of the water - cycle process (the second option is about evaporation, the third is a more general statement but not as comprehensive as the first). The first option encompasses the overall process described in the passage.

Answer:

Water moves around the Earth in a series of steps known as the water cycle.