某历史课本剧中有一场景如下：1917年的某天，陈独秀挥舞《岩声》，向青年学生宣传“民

已知三角形ABC中，AB=AC，点A，B，C在以O为圆心的同一个圆上，圆心O到BC的距离为3cm，圆的半径为7cm，求腰长AB．

500个2.05相加的和是（    ）。

用括号中单词的适当形式填空。

1. Please be quick, or you       (be)late for the meeting.

2. The bus       (leave)when I got to the bus stop.

3. The dictionary must       (take)good care of.    

4. Either you or she        ( have) made a wrong decision.

5. Joanna received many        (gift) when graduating from middle school.

6. Alex is        (fourth) years old and is taken good care of in the kindergarten.

7. Whose school uniform is that on the chair, yours or       (his)?  

8. It was       (difficulty) for human beings to protect weather in the past.  

9. There is a beautiful       (paint)on the wall in each room of my house.  

10. You need to explain your opinions quite        (clear) when having a debate.

侧护板有什么作用？

抗组胺药H₁受体拮抗剂药理作用是（）

A.有相反的药理作用，发挥生理对抗效应

B.和组胺起化学反应，使组胺失效

C.能与组胺竞争H₁受体，使组胺不能同H₁受体结合而起拮抗作用

D.能稳定肥大细胞膜，抑制组胺的释放

E.以上都不是