A:
B:- 43.5
C:+ 43.5
D:+ 67.7
He spent two hours ____ (watch) the game show last night.
如图(甲)、(乙)所示是由相同的滑轮组装的滑轮组,甲 乙两人分别用两装置在相等时间内将质量相等的重物匀速提升相同的高度,空气阻力、摩擦、滑轮和绳子的质量均不计,下列说法正确的是()
—Because my dog was ill. I had to it at home.
如图为人的屈肘动作示意图,与此有关的叙述正确的是( )