人工遮蔽有两种分类。以下遮蔽方式中，不属于伪装网遮蔽方式的是（）。
A.水平遮蔽
B.垂直遮蔽
C.掩盖遮蔽
D.烟雾遮蔽
参考答案：D
— Sorry, Professor Smith. I didn't finish the assignment yesterday.
— Oh, you _____ have done it as yesterday was the deadline. [ ]
A. must
B. mustn't
C. should
D. shouldn't
引起发电机出口继电器动作的原因有哪些？
