--It is a long time since I saw my sister.
-- her this weekend?
| A．Why not visit |
| B．Why not to visit |
| C．why not visiting |
| D．why don＇t visit |
Can you solve such problems ___raised by the audience?
| A．what were | B．as were | C．that were | D．which were |
We often think of the days ___we spent together on the island.
| A．when | B．which | C．in which | D．during which |
Air, _ __we breathe every day, is around us all the time.
| A．that | B．/ | C．which | D．it |
The radio set __ _ last week has been out of order.
| A．I bought | B．I bought it | C．which I bought it | D．what I bought |
He is a man of great knowledge, ___much can be learned.
| A．in whom | B．about whom | C．from whom | D．of whom |