Yesterday I met my old friend which gave me a big surprise.A. in returnB. on purposeC.

问题补充：

Yesterday, I met my old friend , which gave me a big surprise.

A. in return

B. on purpose

C. by chance

D. in case

答案：

A. in return

B. on purpose

(答案→)C. by chance

D. in case

解析：短语辨析. A.作为报答 B. 有目的的;C.意外的 D.万一.句意:昨天我偶然遇到了我的老朋友,给了我一个大大的惊喜.选C.