--Your effort is sure to pay -Thank you for your encouragement.A. offB. forC. backD. do

问题补充：

--Your effort is sure to pay

---Thank you for your encouragement.

A. off

B. for

C. back

D. down

答案：

(答案→)A. off

B. for

C. back

D. down

解析：句意：你的努力一定会得到回报的。谢谢你的鼓励。pay off得到回报，pay for付款，pay back 偿还，所以选A。