按财政支出的经济性质分类，财政支出可分为( )。 A．购买性支出 B．预防性支出

下列离子方程式中正确的是 [ ]

A．碳酸氢铵溶液中加入过量氢氧化钠溶液：HCO₃^- + OH^- = CO₃^2-+ H₂O

B．氯化铝溶液中加入过量氨水：Al³⁺ + 4NH₃·H₂O = AlO₂^-+ 4NH₄⁺+2H₂O

C．二氧化氮通入水中：3NO₂ + H₂O = 2H⁺ + 2NO₃^- + NO

D．氯气通入水中的反应：Cl₂+H₂O = 2H⁺+ Cl^- + ClO^-

能保护人体防止感染乙型肝炎的是（）

A.抗-HBs

B.DNA抗体

C.HBeAg

D.抗-HBC

E.DNA多聚酶

根据句子的语境，填写适当的连接词。

1. He said_________he had finished his homework in time.

2. I really don't know________she is.

3. I don't know________he didn't attend the meeting that day.

4. Tom asked me__________I had received his email.

5. He wondered_________he could get it or not.

6. She wants to know________many books he has sent to to you.

7. Do you remember_________I told you last time?

8. Do you know_________bag it is?

9. I wonder_________is your favorite in these books.

10. He asked me_________these fruits cost.

减小换流器特性谐波输出的主要方法有增加换流器的（）和装设（）两种。

原型生命周期提供了一种用原型化完成______的完整的方法。