The newspaper _____ it'll be sunny tomorrow. [ ]
A. tells
B. says
C. writes
答案:B
若等差数列{an}的前n项和为Sn,且a2+a3=6,则S4的值为( )
A.12
B.11
C.10
D.9
屏气试验是测试心肺功能的简易方法,深吸气后进行最大限度屏气,其正常值应在多少秒以上()
A.15
B.20
C.30
D.60
E.90