You should get down to your study from now on.Please________what is of great importance for

your future development . [    ]

A. concentrate on  

B. depend on

C. put on  

D. take on

对艾滋病病人产生歧视的根源在于（）

A.对HIV传播途径的无知

B.机会感染造成躯体损害

C.输入被HIV感染的血液制品

D.卖淫、嫖娼是社会丑恶现象

E.多性伴侣行为