They have been skating __________.
| A．for three hours | B．since three hours ago |
| C．three hours ago | D．since three hours |
People have learned a lot from
studies．
| A．science | B．scientific |
| C．scientist | D．sightseeing |
The computer was invented in the 20th
| A．sentence | B．center |
| C．concert | D．century |
The boy often got into
with the police.
| A．through | B．terrible |
| C．trouble | D．Trousers |
Please remember to
the cat before you leave.
| A．feed | B．foot |
| C．food | D．find |
John' s mother is a
| A．stop | B．shop |
| C．soup | D．soap |