He never（）（后悔做过的事情）.

What is the only foreseeable threat to the lumber industry?A．The cost of cutting down large trees.B．The threat of the spruce budworm.C．The rising number of imported workers.D．The lack of physically fit employees. 点击查看答案

作为保温材料，采暖期间水泥纤维板重量湿度的允许增量为（）%。

A.3
B.5
C.7
D.10

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