生活中常见的三种物质：①柠檬汁，②肥皂水，③食盐水。柠檬汁能使紫色石蕊试液变红，

试分析造成输灰支线输灰时间延长的原因有哪些？

用被减数减去差的方法可以验算减法。[ ]

用 be( am,  is,  are) 的适当形式填空。  

1. Excuse me! ______ this your ruler?

2. What______ those?______ they pictures?

3. This ______his backpack. Where ______ mine( 我的 ) ?

4. I______ in Class Three. ______ you in  Class Three, too?

5. ______ these her English books?

6. Those ______ their apples. Where______his apples?

7. She ______ eleven. How old______ that boy?

8. He ______ my friend.______ your friend a boy or a girl?

9. —______ those maps?

    —No, they______ not.

10. These ______ your bananas, Jim. Here you

六味地黄汤宜选用（）。

A.鲜地黄

B.生地黄

C.熟地黄

D.生地炭

E.熟地炭

试述社会交换论的主要观点及其局限性。