Question

    You may say that rain comes from clouds, but you can also say that rain is clouds.1., you should know the mechanism through which water moves from the Earth to the atmosphere and back again.

Dew point is the temperature at which water vapor begins to condense (凝结) and becomes water droplets that can fall as rain. Dew point can vary anywhere from the 30s (Fahrenheit) to, on rare occasions, the 80s.

2.. Once the air has cooled past the “dew point", it condenses around a nucleus, which are usually tiny particles of dust, smoke or even salt that are floating in the air. Then tiny water droplets are formed.3.. If you pay close attention to clouds in the sky, you'll see char they’re constantly shrinking and growing,

Water vapor that has formed clouds is on its way to becoming rain, bur it's not there yet. For now, the water droplets are 80 tiny that the air currents keep them in the air, just as swirling particles of dust can stay in the air.4..

When water droplets combine with one another, they become heavier than the uplift of the air around them. Eventually they fall down through the cloud as rain.5.They attract more water vapor to themselves and grow quickly until they're heavy enough to fall as snow.

A.Rain cloud is formed when there is enough water in the air

B.As warm air rises with the water vapor it contains, it cools

C.If you are curious about what kind of cloud will become rain

D.Sometimes the droplets rise high enough to freeze into ice crystals.

E.The tiny water droplets that initially form are what you see as clouds

F.If you want a better understanding of why rain comes down from clouds

G.As those droplets continue to rise, they have two ways to come back to Earth

Answer

1.F

2.B

3.E

4.G

5.D

【解析】

本文是一篇说明文。文章介绍了雨云是怎么形成的。

1.根据第一段的You may say that rain comes from clouds, but you can also say that rain is clouds.(你可能会说雨来自云，但你也可以说雨是云)可知，本文主要介绍雨云是怎么形成的，F项If you want a better understanding of why rain comes down from clouds (如果你想更好地理解为什么雨从云上落下)围绕这个主题，且承接下文。故选F。

2.通读本段及空后的Once the air has cooled past the“dew point", it condenses around a nucleus, which are usually tiny particles of dust, smoke or even salt that are floating in the air. (一旦空气冷却过了“凝结点”，它就会在原子核周围凝结，而原子核通常是漂浮在空气中的灰尘、烟雾甚至盐的微粒)可知，本段主要讲述雨云的形成原因，B项叙述的是雨云形成的最初状况，选项中的it cools和has cooled相呼应，且语义As warm air rises with the water vapor it contains, it cools (当热空气与它所含的水蒸气一起上升时，它就变冷了)顺承下文。故选B。

3.根据上句Then tiny water droplets are formed.(然后形成微小的水滴)中关键信息词form可知，此处就初步形成的水珠展开叙述。选项中的droplets和上句相吻合，且语义The tiny water droplets that initially form are what you see as clouds(最初形成的小水滴就是你看到的云)承上启下。故选E。

4.根据下文Eventually they fall down through the cloud as rain.(最终它们以雨的形式穿过云层落下)及They attract more water vapor to themselves and grow quickly until they're heavy enough to fall as snow. (它们吸引了更多的水蒸气，并迅速成长，直到它们重到可以像雪一样落下)可知，此处讲述了两种降水形式。故G项As those droplets continue to rise, they have two ways to come back to Earth (随着这些水滴继续上升，它们有两种方式返回地球)符合语境。故选G。

5.根据下文They attract more water vapor to themselves and grow quickly until they're heavy enough to fall as snow. (它们吸引了更多的水蒸气，并迅速成长，直到它们重到可以像雪一样落下)可知，D项Sometimes the droplets rise high enough to freeze into ice crystals. (有时水滴上升到足以冻结成冰晶)紧接其义，语义顺承。故选D。