---- Mummy, can I go out for a play for a while? ---- Yes, if you _______. But make sure you e back before 8:00. A. shall B. will C. must D. could 答案:C如图所示,一根重8N的均匀直棒AB,A端用绳吊在固定点0,用一沿水平方向的力F=6N作用于B端,使棒处于平衡状态,则绳与竖直方向的夹角为( sin370=0.6 cos370=0.8 ): A 300 B 370 C 450 D 600