21. He decided not to attend her birthday party________he had been invited to.
| A．as if | B．even though | C．because of | D．Since |
It was an agreement, ______ could not be changed.
| A．of which details | B．whose the details |
| C．the details of which | D．all whose details. |
The shopkeeper did not want to sell for ______ he thought was not enough.
| A．what | B．which | C．where | D．how. |
Helen was much kinder to her youngest child than she was to the others, _____, of course, made the others unhappy.
| A．which | B．that | C．what | D．who |
The reason why he was late was _______ he had take a wrong bus.
| A．because | B．whether | C．when | D．that |
The school ______ I visited last year was not the one _______ I once worked.
| A．which; where | B．which; which |
| C．where; which | D．where; where |