一个集合由8个不同的元素组成，这个集合中包含3个元素的子集有（） (A)56个 (B)256个 (C)336个 (D)512个
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根据下列短文，回答下列各题。 During the SUmmer session there will be a revised schedule of
A. To tell campus personnel of the new library services．
B. To announce the new movies on campus this summer．
C. To notify university people of important schedule changes．
D. To remind students to validate(使生效)their identification cards．
He’S working hard for fear that he_________．
A. should fall behind
B. fell behind
C. may fall behind
D. would fall behind
设集合M={x|x≥-3}，N={x|x≤1}，则 M ∩ N=（） (A)R (B)(-∞，-3]u[1，+∞) (C)[-3，-1] (D)φ
The case_______．
A. lay fight on one side of ashelf
B. was right behind as oldbrown-looking case
C. was between two highshelves
D. was among the hundreds ofcases
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