Question

【题目】—Why you (look) at the sky?
—Because there is a big plane.

Answer 1

【答案】are；looking
【解析】句意：—你为什么看天空？—因为有一个大飞机。该句子是现在进行时，其结构是：be+doing，主语you第二人称，因此be动词用are，所以答案是are，looking。