There is no doubt _____ short sight is a serious problem among the youth of our country.

A．which

B．whether

C．what

D．that

目前最强的抗绿脓杆菌抗生素是：（）

A.鲁卡因青霉素

B.羧苄青霉素

C.先锋霉素IV

D.头孢他啶