规模经济使得通讯基础设施产业具有（）的特征。
A、行业垄断
B、自然垄断
C、垄断竞争
D、寡头垄断
参考答案：B
单词拼写。
1. This is our _____ (教室). We clean it every day.
2. I am very_____ (高兴) to help you.
3. They come from _____ , They are _____ (英国).
4. The girl loves _____ (跳舞).
5. She is in the _____ (阅读) Club.
6. He is a good singer. He sings _____ (好).
7. Simon is _____ (有趣)，I like him very much.
8. I am good at _____ (游泳).
骨折血肿机化演进期大约需要（）
A.3天
B.5天
C.1周
D.2周
E.3周
