We were all worried over _______ you were sick.

We can go on Tuesday or Friday，        you preler.

(2014·东北三校模拟)We had just covered half the journey________the engine failed and we could do nothing but wait for help.

There is no way of knowing why one man makes an important discovery ______ another man, also intelligent, fails.

Schools in the south tend to be better equipped，_______those in the north are relatively poor.