_____ from the top of the tower, the south foot of the mountain is a sea of trees .
| A．Seen | B．Seeing | C．Having seen | D．To see |
2. ______was known to them all that William had broken his promise______ he would give each of them a gift.
| A．As, which | B．What, that | C．It , that | D．It , which |
3. —How long are you staying there?
— _____depends.
| A．It | B．Anything | C．This | D．Everything |
4. I hate _______ when young people speak to the elderly in a rude way.
| A．this | B．that | C．it | D．One |
5.Is ____ necessary to complete the design before National Day?
| A．this | B．that | C．it | D．he |
6.I don’t think ____ possible to master a foreign language without much memory work.
| A．this | B．that | C．its | D．it |