By coincidence, oil paints were developed at the time when technique of perspective was u

发布时间：2020-08-17 01:38:21

By      coincidence, oil paints were developed at the time when     technique of perspective was used.
A. a ;  the     B \ ; a    C. \; the   D. a; a

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解析：考查冠词。第一空的固定词组by coincidence偶然；第二空特指透镜，望远镜的技术。故C正确。
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