按照OSI参考模型，支持无连接数据保密的层包括（）
A.链路层
B.网络层
C.传输层
D.会话层
E.表示层
参考答案：A, B, C, E
After Chang’e-3 landed on the moon on Dec 14, China became the third country _________ this after the US and the former Soviet Union.
A．having achieved
B．achieving
C．achieved
D．to have achieved
离心泵可用在输送腐蚀性或悬浮液的场合。
