墩身模板及拉筋应经计算确定,拉筋应采用()并套双螺母。
参考答案:光圆钢筋
I ______ her, but I never could. [ ]
A. ought to help
B. must help
C. must have helped
D. ought to have helped
天空中两颗星相对于一望远镜的角距离为4.84×10-6弧度,由它们发出的光波波长λ=5.50×10-5cm,若能分辨出这两颗星,望远镜物镜的口径至少为( )cm。
A.10.1 B.13.9 C.50.4 D.100.7