After 15 years in the USA, he finally decided to American citizenship.
A. concentrate on
B. apply for
C. put off
D. lead to
网友回答
A. concentrate on
(答案→)B. apply for
C. put off
D. lead to
解析：A. concentrate on全神贯注于，B. apply for申请， C. put off推迟，D. lead to导致，句意：--在美国15年后，他最后决定申请美国公民。根据句意选B。