_______will Mr. Black be able to regain control of the company.

A．Only by working hard

B．Only he works hard

C．With hard work

D．Only if work hard

对疟疾有一定效果的抗生素是（）

A.氯霉素

B.多西环素

C.甲砜霉素

D.链霉素

E.米诺环素