It is _____ we do —- you and I ____ changes the world.

.I soon found that the work I was doing hadalready been done by someone else – ________, I was wasting my time.

College students want to find jobs ________ they can receive not only good pay but also a sense of satisfaction.

The inventor was determined to go on with the experiment_______countless failures.

Just now, this girl was noticed to enter the video shop, ____ some latest DVDs and leave in a hurry. [ ]