邮政通信的服务方针是迅速、准确、（）、方便。
参考答案：安全
道德的评价标准是以（）为标准。
A.真假
B.是非
C.善恶
D.正邪
The two elements()water is made are oxygen and hydrogen.
A. that
B. which
C. of which
D. with which
