下列几种现象中，动量不守恒的是 A．在光滑水平面上两球发生碰撞 B．车原来静止在

用所给动词的正确形式填空。

(1) — Why isn't Jim here? 　　　　　

     — He's busy. He __________ (take) care of his aunt's baby at home now. 　　

(2) — What's Mr. Clarke going to do tomorrow? 　　　　　

     — He'll go fishing if it __________ (not rain). 　　

(3) Linda __________ (make) a lot of friends since she came here last autumn. 　　

(4) — Did Jack finish__________ (clean) the house this morning? 　　　　　

     — Yes, he did. 　　

(5) — Have you heard of the Great Wall, Mr. Read? 　　　　　

     — Yes, I have. It's a place of great interest in China. 　　　　　　　

     It _________ (build) thousands of years ago.

我国宪法规定，劳动和受教育，既是公民的基本权利，又是公民的基本义务。这体现了公民权利和义务一致性的[ ]

A．制约性  

B．对等性   

C．对立性   

D．合一性

子宫脱垂I度重型是指

A．宫颈距处女膜缘＞4cm

B．宫颈距处女膜缘＜3cm

C．宫颈达坐骨棘水平

D．宫颈达处女膜缘

E．宫颈距处女膜缘＜4cm

普通平板玻璃的主要组成成分及其作用？