To his parents’ great joy, all their son’s years of hard work finally .
A. set off
B. paid off
C. took off
D. got off
网友回答
A. set off
(答案→)B. paid off
C. took off
D. got off
解析：考察词组。Set off 引爆 pay off取得回报 take off 起飞，腾飞 get off下车
句意为，令他父母感到高兴的是，他们儿子这么多年的努力终于取得了回报。