It suddenly occurred to him __________ he had left his keys in the office.
| A．whether |
| B．where |
| C．which |
| D．that |
Was it on a lonely islandhe was saved one month after the boat went down.
| A．where |
| B．that |
| C．which |
| D．what |
John's success has nothing to do with good luck. It is years of hard work _______has made him a great scientist today.
| A．that |
| B．when |
| C．which |
| D．why |
It was 80 years before Christopher Columbus crossed the Atlantic______ Zheng sailed to East Africa
| A．when |
| B．that |
| C．after |
| D．since |
It was not until near the end of the letter ______ she mentioned her own plan.
| A．where |
| B．that |
| C．why |
| D．when |
It was only after he had read the papersMr. Gross realized the task before him was extremely difficult to complete.
| A．when |
| B．that |
| C．which |
| D．What |