Someone is ringing the doorbell. Go and see _______.
| A．Who is he | B．who he is | C．Who is it | D．who it is |
David is such a good boy _______ all the teachers like him.
| A．that | B．who | C．as | D．whom |
______ is mentioned above that the number of the students in senior school is increasing.
| A．Which | B．As | C．That | D．It |
______ is mentioned above, the number of the students in senior school is increasing.
| A．Which | B．As | C．That | D．It |
_______ is known to everybody that the moon travels round the earth once every month.
| A．It | B．As | C．That | D．What |
_____ is known to everybody, the moon travels round the earth once every month.
| A．It | B．As | C．That | D．What |