明沟排水的坡度一般不小于（）。A、0.4% B、1.4% C、2.4% D、4.0%

完成下列单位换算：

（1）______t=0.6kg=______g=______mg；

（2）2.7×10³kg/m³=______g/cm³；

（3）100ml=______cm³=______m³．

写出下列化学符号或符号所表示的意义。

(1)空气中含量最多的元素是____；

(2)地壳里含量最多的元素是____；

(3)地壳里含量最多的金属元素是_______；

(4)生物细胞里含量最多的元素是______；

(5)相对原子质量最小的元素是_____；

(6)1个钠原子_____；

(7)3个硫原子_______；

(8)C1______________、____________ ；

(9)4Mg____________。

阅读理解。

      At exactly eleven Sir Percival knocked and entered, with anxiety and worry in every line of his face.

This meeting would decide his future life, and he obviously knew it.

     "You may wonder, Sir Percival," said Laura calmly, "if I am going to ask to be released (免除) from

ray promise to marry you. I am not going to ask this. I respect my father's wishes too much. "

     His face relaxed a little, but one of his feet kept beating the carpet.

     "No, if we are going to withdraw.(退出) from our planned marriage, it will be because of your wish,

not mine. "

     "Mine?" he said in great surprise. "What reason could I have for withdrawing?"

     "A reason that is very hard to tell you," she answered. "There is a change in me. "

     His face went so pale that even his lips lost their color. He turned his head to one side.

     "What change?" he asked, trying to appear calm.

     " When the promise was made two years ago", she said, " my love did not belong to anyone. Will you

forgive me, Sir Percival, if I tell you that it now belongs to another person?"

     "I wish you to understand", Laura continued, "that I will never see this person again, and that if you

leave me, you only allow me to remain a single woman for the rest of my life. All I ask is that you forgive

me and keep my secret."

     "I will do both those things, " he said. Then he looked at Laura, as if he was waiting to hear more.

     "I think I have said enough to give you reason to withdraw from our marriage,',she added quietly.

     "No. You have said enough to make it the dearest wish of my life to marry you, " he said.

1.How did Percival feel during his meeting with Laura?

A. Angry.

B. Calm.

C. Nervous.

D. Excited.

2.We can learn from the passage that _____.

A. Laura had once promised to marry Percival

B. Laura's father wished to end her marriage

C. Percival had been married to Laura for two years

D. Percival asked to be released from the marriage

3.The passage is probably taken out of_____.

A. a novel

B. a report

C. a diary

D. an essay

如果在1930年从中国洛阳出发，前往美国加拿大和苏联，沿途看到的不会是

A．中国：“白骨遍田野，千里无人烟”

B．美国：经济繁荣，工业生产高涨

C．加拿大“人民要求脱离英国的呼声高涨

D．苏联：机器轰隆，但人们衣着简单

如果系统中的所有作业是同时到达的，则使作业平均周转时间最短的作业调度是______。