The parents were in search their son who was lost when the two countries were war.A. of;

问题补充：

The parents were in search their son who was lost when the two countries were war.

A. of; in

B. of; at

C. for; at

D. for; in

答案：

A. of; in

(答案→)B. of; at

C. for; at

D. for; in

解析：考查固定词组。固定词组in search of 寻找…；at war在战争时；句意：当这两个国家处于战争状态的时候，这对父母正在寻找失踪的的儿子。故B正确。