1.We thought that it is a good idea. It does not cost much, but we can still learn a lot.
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答案：thought→think 考查动词的时态。后面句中用的都是一般现在时。
2．When summer came, we will invite the students to pick the watermelons.
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答案：came→comes 考查动词的时态。主句用一般将来时，时间状语从句用一般现在时。
3．When I was young, I would went to the bridge, waiting for my father from work.
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答案：went→go 考查动词的时态。情态动词后用动词原形。
