造成电信网络运营业具有较高的市场退出壁垒的因素是( )。
A．产品同质
B．产品异质
C．沉没成本大
D．无沉没成本
参考答案：C
根据句意和首字母提示补全单词。
1. I'm in Class 2. He's in Class 2. We're in the s______ class.
2. I can l______ a lot about Chinese history.
3. His f______ food is chicken.
4. Her brother w______ to be an artist.
5. Do you want to go to a m______.
6. Wang Ming likes t______ but he doesn't like documentaries.
7. My brother likes action movies. He thinks it's e______.
什么是湿碰湿工艺？
