--Have you got the leaving time of the train for me?

---Yes, but you’d better ____of it by yourself.

A．make sure

B．be sure

C．to make sure

D．be certain

咨询的质量改进工作，( )。

A．不能是完全的封闭循环
B．具有一次性的特点
C．具有预测性
D．具有时效性