AIDS is said __________ the biggest health challenge to both men and women in that area over the past few years.

A．that it is

B．to be

C．that it has been

D．to have been

某加碘食盐包装袋上标有“忌高温蒸炒”，由此判断下列说法中正确的是（　　）

A．此食盐是纯净物

B．所加含碘物质受热易分解

C．食盐中加入了碘单质

D．加碘食盐难溶与水