用HPLG法测得某药保留时间为12.54分钟，半高峰宽3.0mm(低速5mm/min

在实施体育课程的过程中，所谓从上至下的策略即是以（）和（）为中心的逐渐推进实施的策略。

已知f（x）在（-∞，+∞）内是减函数，且a+b≤0，则下列各式正确的是______．（填序号）

①f（a）+f（b）≥f（-a）+f（-b）；    ②f（a）+f（b）≤f（-a）+f（-b）；

③f（a）+f（b）≤-f（a）-f（b）；     ④f（a）+f（b）≥-f（a）-f（b）．

单词拼写。

1. W             so long time really made him angry.

2. Tom won't go to Hainan. Larry will go, i            .

3. Last month, we had a talent show which was a great s            .

4. I like T            , the day before Friday best.

5. Take your coat, there will be w              tomorrow.

6. My brother doesn't feel scared when he is left a            .

7. Do you know who i              the computer first?

8. I like pop music because it makes me r             .

9. At the b             of the class, all the students are noisy.

10. After his father's d             , his life became much harder.

形成酸雨危害的主要污染物之一是[ ]

A．氧化碳

B．二氧化硅

C．氧化氮

D．氟氯烃

常见的褐藻有哪些？