把10克盐放进200克水中,这时盐和盐水质量的比是1:20.______.(判断对错)
10:(10+200)=1:21,
答:盐和盐水质量的比是1:21;
故答案为:×.
在下列各句的空白处填入一个最恰当的单词。
1. I opened the box quickly, but it was _____ .
2. I hadn't taken the keys with me, so I _____ myself out.
3. Don't be nervous! Jump _____ the sand.
4. You can't _____ her. She's much too clever for that.
5. My grandfather is a _____. He has a big farm.
6. Henry didn't _____ until he was over fifty years old.
7. The cartoon Snow White has a happy _____.
8. Children in the USA have a _____ party on Halloween ( 万圣节).
9. All the frightened people_____ from the fire.
10. Can you give me a _____ of paper?
以下()不是液压马达的基本性能参数。
A、排量
B、输出转矩
C、输出转速
D、输出压力