单选题：—How long is it _____ we last met?—About five years. You h..

Good friends __________ we are, I still find her difficult to understand at times.[ ]A. as B. becauseC. thoughD. unless

The problem of the present world is that those who are imaginative have little experiencethosewho are experienced have weak imagination. [ ]A. unlessB. althoughC. becauseD. while

________you know how to manage your time,you can try to work and look after the children well meanwhile.[ ]A. If onlyB. Even thoughC. As soon asD. Now that

—You seem to have had that car for years.—Yes, I should sell it ________ it breaks down.[ ]A. whileB. afterC. untilD. before

Most whales must come up for air after several minutes, ______ a few can stay under water for an hour or more.[ ]A. whileB. orC. forD. so