A.1:1
B.2:3
C.3:2
D.9:4
答案:D
How many months ____________ in a year? [ ]
A. are there
B. is there
C. have
D. were there
机械连接接头面积在受拉区占受力钢筋总截面积的允许百分率的最大值为()
A.10%
B.25%
C.50%
D.55%