题目内容

【题目】It's the second time that I __________ in Beijing. What great changes! It's years since I __________ here last time.

A. went; had left B. have been; left

C. had been; left D. have been; had left

【答案】B

【解析】句意:这是我第二次到北京。变化真大啊！自从上次离开这里有数年了。考查时态。在句型It is the +序数词+ time that...中that从句中用现在完成时；在句型It is+一段时间+Since...中since引导的从句中用一般过去时。

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【题目】The planet is getting greener, and we are responsible. Carbon dioxide generated by human activities is promoting photosynthesis (光合作用) and causing a beneficial greening of the Earth’s surface.

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