About the time the three climbers were halfway down, clouds blotted out the sun.

当3位登山者下到半山腰的时候，云层遮住了太阳。

《柯林斯英汉双解大词典》

Over the past three weeks, the storm clouds have gathered again over the government.

在过去三周里，不祥的阴云再次笼罩了政府。

《柯林斯英汉双解大词典》

If the birds have not flown for three years, they will soar into the clouds. If they have not sung for three years, their songs will take everyone by surprise.

三年不蜚，蜚将冲天；三年不鸣，鸣将惊人。

《新英汉大辞典》

So which of these three clouds on the horizon worries me the most?

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But there are three black clouds over this sunny scene.

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Visibility was three miles, but the clouds were at 400 feet.

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