下列情况中()是一套连续沉积的含有煤或煤层的沉积岩层或地层。
A.含煤岩系
B.煤的结构
C.煤的构造
D.煤层
参考答案:A
已知全集U={x∈N|0<x≤6},集合A={x∈N|1<x<5},集合B={x∈N|2<x<6}
求(1)A∩B
(2)(CUA)∪B
(3)(CUA)∩(CUB)
I was really anxious about you. You ______ home without a word.
A.mustn’t have left
B.shouldn’t have left
C.couldn’t have left
D.needn’t have left