拖拉机直线行驶时,差速器行星齿轮()。
A、既公转、也自转
B、只公转、不自转
参考答案:B
Not until the mid-term approached ____________ how much time I had wasted.
A.did I realize
B.didn’t I realize
C.I didn’t realize
D.I realized
SMTP服务利用______连接传送数据,而SNMP使用的传输层协议是______。
A.IP B.UDP C.TCP D.IMCP