以生物碱为主要成分类型的药材是（） A.鸡血藤 B.降香 C.钩藤 D.

根据句意和提示写出单词，完成句子。

1. I'd love to join you in the camping, but I have _____ (允诺) to go cycling with John.

2. Look at the sign!We are not _____ (允许) to park cars here. 3.Would you please help me look after

    my dog while I am _____ (离开)?

4. Our Maths teacher spent 2 hours _____ (解释) the tough problems to us like this.

5. I can't tell you  _____ (是否) it's a good book or not without reading it.

6. It's over four months since we Chinese people celebrated our Party's n_____ birthday on July 1st.

7. Look at the dark clouds in the sky. P_____ it is going to rain in the afternoon.

8. Kung Fu Panda II is a fantastic film and I want to see it, but I haven't made a d_____ now.

9. Don't be nervous. If you try to be r_____ in the exam, you will get high marks..

10. Grandma has got a toothache. She is at the d_____.

11. There are so many good programmes that I can hardly make a _____ (choose) among them.

12. Lucy and Linda didn't tell us the news. They wanted to keep the secret to _____ (they).

13. The boy hates to follow others and likes doing everything _____ (different)

14. Can you tell me why the twins are quarrelling more _____ ( noise) than usual?

15. She is grateful to you for giving her so many _____ (value) advice on how to cook.

下列分类正确的是（　　）

A．灭火方法：降低着火点、隔离可燃物、隔绝O₂

B．常见的化肥：铵肥、磷肥、钾肥

C．常见的合金：不锈钢、黄金、黄铜

D．人体内供能物质：蛋白质、油脂、糖类

下列选项中不属于桌面检查中常量检查内容的是______。

A．常量的取值
B．常量的类型
C．常量的引用率
D．定义与引用的一致性

对烟叶燃烧性描述不正确的是（）。

A、钾有利于烟叶的燃烧

B、氯有利于烟叶的燃烧

C、燃烧强者较为理想

D、阴燃值在2秒以上者为不熄火烟叶

（10分）如图，足够长的平行玻璃砖厚度为d，底面镀有反光膜，顶面涂有长为d的遮光物质AB。一束光线以45°的入射角由遮光物质A端入射，经底面反射后，恰能从遮光物质B端射出。已知真空中的光速为c，求：

①光线在玻璃中的传播速度；

②为使各种角度入射的光线都不能由顶面射出，遮光物质AB至少多长？