A new material______we have good reason to be optimistic.A、developedB、being dev

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问题 A new material______we have good reason to be optimistic.

选项 A、developed
B、being developed
C、was being developed
D、was developed

答案 B

解析此句考查的是独立主格结构，比较难。由后句时态可断定前面不应该用过去时，故排除A、C、D选项。译文：一种新的材料正在研发之中，我们完全有理由保持乐观。

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