免疫功能主要是____________、___________和_____________。
参考答案：免疫防御；免疫自稳；免疫监视
-How much did this CD __________ you, Sally?
-I got it for 5 dollars.[ ]
A. use
B. spend
C. take
D. cost
小浪底水利枢纽位于______流域上．
