单选题
After 15 years in the United States, he has finally decided to______American citizenship.
A．concentrate on B．apply for C．look out for D．appeal on
【正确答案】
B
【答案解析】[解析] 本题考查的是动词词组。concentrate on集中注意力于；apply for申请；look out for留心，期待；appeal on呼吁，要求，诉诸。在美国待了15年以后他最终决定申请美国国籍。