钢丝绳的大接头插接长度是绳径()倍,小接头插接长度是绳径()倍。
A.40-50;20-40
B.20-40;40-50
C.30;30
参考答案:B
已知等差数列{an}中,a7+a8=16,a4=1,则a11=( )
A.15
B.30
C.31
D.64
Mary waited for a reply, but__________came.
A.no one
B.none
C.nothing
D.neither