It was not until the subprime loan crisis(次贷危机) ____ great damage to the American financial system that Americans ____ the severity of the situation.
| A．caused, realized | B．had caused, realized |
| C．caused, had realized | D．was causing, had realized |
You can't borrow books from the school library __________ you get your student card.
| A．before |
| B．if |
| C．while |
| D．as |
She had just finished her homework __________ her mother asked her to practise playing the piano yesterday.
| A．when |
| B．while |
| C．after |
| D．since |
The girl had hardly rung the bell __________ the door was opened suddenly, and her friend rushed out to greet her.
| A．before |
| B．until |
| C．as |
| D．since |
As is reported, it is 100 years __________ Qinghua University was founded.
| A．when |
| B．before |
| C．after |
| D．since |
He had no sooner finished his speech __________ the students started cheering.
| A．since |
| B．as |
| C．when |
| D．than |