– Amazing! You have won the first prize in the national English speech contest!– I’m luck

问题补充：

– Amazing! You have won the first prize in the national English speech contest!

– I’m lucky that all my efforts have finally paid off.

A. must

B. may

C. can

D. should

答案：

A. must

B. may

C. can

D. should

解析：--真是令人惊讶！你竟然在全国英语演讲比赛中获得一等奖！--我很幸运所有的努力都最终有了回报。Should have done表示惊讶的语气，must have done过去一定做了，may have done过去可能做了，can have done用于疑问或否定句中，选D。