问题补充:
that he isn’t adequate to the present job, he devotes all his spare time to studying professional knowledge.
A. Concern
B. To concern
C. Concerned
D. Concerning
答案:
A. Concern
B. To concern
(答案→)C. Concerned
D. Concerning
解析:考查形容词做状语,concerned:对…担心,关心,是形容词做状语,表示状态。句意是:担心他不能适合现在的工作,他把所有的时间都用来学习专业知识。选C。