A:2
B:3.333
C:﹣π
D:4
He jumps________than________in his class.
A.甲图省力,机械效率甲图大 B.甲图省力,机械效率一样大
C.乙图省力,机械效率乙图大 D.乙图省力,机械效率一样大
理由:____.