______ polar bear population is ______ sensitive topic for the Canadian government, which allows limited hunting.
| A．A; the | B．A; a | C．The; the | D．The; a |
He has three brothers, ________ is a doctor．
| A．all of them | B．all of whom | C．none of whom | D．both of them |
He never reads anything _______ is not worth reading．
| A．as | B．which | C．who | D．that |
―When was the house built?
―It was built in 1949 _______ the PRC was founded．
| A．which | B．that | C．what | D．when |
________ is known to everybody, the moon travels round the earth once every month．
| A．It | B．As | C．That | D．What |
This is Mr．Smith, ________ I think has something interesting to tell you．
| A．who | B．whom | C．that | D．/ |