Frank _________work to do. [ ]
A. has many
B. has much
C. have a lot
D. have a lot of
答案:B
In China,it is a traditional________to show respect to ancestors during the Qingming Festival.
A.belief
B.custom
C.strength
D.principle
如图所示,一根绳子跨过定滑轮,左端系在运动员身上,右侧绳子握在运动员手中,已知运动员质量为50kg,他手拉绳使自己以2m/s2的加速度匀加速下降,不计绳子质量及绳子及滑轮之间的摩擦,运动员手对右侧绳的拉力多大?