如果代数式4x-2y+5的值为7，那么代数式2x-y+1的值为[ ]
A.2
B.3
C.-2
D.4
答案：A
什么是统计分布数列？
-Dad，why should I stop _________ computer games?
-It’s quite clear,my boy，I’m afraid you ________ .[ ]
A. to play; must
B. playing；have to
C. to play；can
D. playing; may
