A large number of engineers ___ to Africa by our government to help the people there every year.[ ]

A. have sent        

B. will send          

C. are sent        

D. was sent

胸片后前位示左肺门肿块影约3cm大小，边缘有分叶征，伴有左上叶肺不张。应首先考虑的疾病是（）

A.肺结核

B.肺炎

C.结节

D.肺癌

E.肺脓肿