有效指标
参考答案：
内燃机的有效指标是用来评定内燃机性能好坏。以曲轴输出功率为计算基础的性能指标称为有效指标。
根据句意填空，首字母已经给出。
1. When you want to post a letter,you need a s______.
2. You room is u______.You need to clear it up.
3. Edison was so c______that he invented a lot of things.
4. You have collected all different kind of dolls.We can say you have a big
c______
5. Many students have h______such as reading,painting and so on.
在电力线路架设时，什么情况下应装设水平拉线？对水平拉线有什么要求？
