完成文件传输服务的TCP/IP协议是()
A、SMTP
B、FTP
C、SNMP
D、Telnet
参考答案:B
用所给词的适当形式填空
1. There ______ (be) a picture on the wall.
2. Are there ______(some) teachers in the classroom?
3. There ______(be) two pencils and a pen on the desk.
4. In the classroom, there ______ (be) ten students and a teacher.
5. There aren't any ______ (apple) in the box.
单相桥式整流电流电路输入电压为8V,其输出电压为()。
A.3.2V
B.3.6V
C.7.2V
D.8V