问题补充：
Many friends sent me e-mails to me on the birth of my son.
A. celebrate
B. reward
C. express
D. congratulate
答案：
A. celebrate
B. reward
C. express
(答案→)D. congratulate
解析：考查动词辨析。congratulate sb. on sth.祝贺某人某事；celebrate 庆祝(节日) reward报酬，报答；express表达，根据意思，应选D。
