Tom ________ in the library every night over the last three months.[ ]

A. works  

B. worked

C. has been working  

D. had been working

工程咨询领域，要求加强人才队伍建设，逐步形成具有一定特色的行业人才梯队，要求该梯队以（）为主体。

A.行业领军人物

B.复合型人才

C.专业执业人才

D.经验丰富的专家队伍