She had to drop out of school _____ her family couldn’t afford the cost of her education.
I don’t know how it ___________ that our car was bumped from behind.
Nowadays, an increasing number of people have ___________ to the information they need through the Internet.
The development of industry has been ________ gradual process throughout ______ human existence from stone tools to modern technology.
----I’m afraid I’ve broken your cup. ----______________, it was old and I was going to throw it away.
Between the two parts of the concert is an interval, ______ the audience can buy ice-cream.