The fire went on for quite some time _______ it was brought under control.
| A．when | B．since |
| C．after | D．before |
It was totally by chance they discovered the entrance to the underground palace.
| A．when | B．which | C．why | D．that |
The boys by the coach now will take part in the sports meeting of the school next month．
| A．chosen | B．being chosen |
| C．choosing | D．to be chosen |
Schools in the cities are well equipped those in the countryside are poor．
| A．if | B．while | C．so | D．as |
I received a letter，poor spelling made me think it was written by a child．
| A．which | B．that | C．whose | D．who |
The new online library makespossible for students to choose books by smart phone off campus．
| A．it | B．one | C．that | D．this |