The President was among the first to congratulate the scientist ______ his new discovery.

 

　　A.at

 

　　B.in

 

　　C.about

 

　　D.on

 

　　正确答案：D

 

　　答案解析：本题考查介词的固定搭配。congratulate sb on sth：祝贺某人某事。