---It’s a long time _____ I saw you last.

---Yes, and what a pity it is now that it will be a long time _______ we see each other again.

A．before; since

B．since; when

C．since; before

D．when; before

教育实践活动着眼于自我净化、自我完善（）和自我提高。

A、自我改进

B、自我批评

C、自我革新

D、自我进步