Scientists say it may be five or six years ____ it is possible to test this medicine on human patients

dies are ________ by working out Similarly, ourminds are developed by learning

Jimmy is looking forward to the winter holiday.He will visit Beijing________ it begins.

—Guess what? I happened to have met Mark at the party last week.—If my memory serves me correctly, you two ______ each other for almost ten years. [ ]

g has a population of 17 million,________ it one of the largest cities in China