AIDS is said_______ the biggest health challenge to both men and women in the earth over the past four years.

A．that it is

B．to have been

C．that it has been

D．to be

肺炎球菌肺炎的抗菌治疗宜首选()

A．青霉素

B．大环内酯素

C．喹诺酮类

D．头孢菌素类

E．氨基糖苷类