题干
—Such a mistake could have been avoided.
—Unfortunately, he_______the mistake again and again
A：repeated
B：would repeat
C：has been repeated
D：would have repeated
答案(点此获取答案解析）
A
，物体的质量为m，现将物体m从B点沿原路拉回至A点处，拉力做的功至少应为（ ）