_________ the children were having fun, the parents were taking photos of them.
A. When B. If C. While D. Once
Scientists say it may be a few years ______it is possible to test the new medicine on
patients.
A. because B. after
C. since D. before
When he was _______ university student, he wanted to become _________ NBA player.
A. a, a B. an, an C. a, an D. an, a
We are not sure when the rain ________. When the rain ________, we will go on working.
A. will stop, stops B. stops, will stop C. will stop, will stop D. stops, stops
--- How long have you read this book? --- _________ I finished my homework.
A. Until B. As soon as C. Since D. When
We don’t know how important something is _______ we lose it.
A. or B. until C. as soon as D. after
