消防二级网一般为（）手持电台网。
A、多频单工
B、单频单工
C、异频单工
D、单频多工
参考答案：B
根据句意及首字母提示填空。
1. Many students' favorite subject is s_____.
2. W_____ is the fourth day of a week.
3. Please give me an e_____; I am not clear about the problem.
4. Are your teachers s_____ with you m your lessons?
5. I'm s_____ you will do better in your lessons this term.
（）（）（）也是整体设计的重要特征
