The science of computer, _____rapid progress has been made in recent years, is the most important of all science.
Never before ___________ seen anybody who can play tennis as well as Robert.
Jim went to answer the phone. ___________, Harry started to prepare lunch.
Mary and I see each other ___________. but not as often as we used to.
Father ____________ goes to the gym with us although he dislikes going there.
Gun control is a subject ___________ Americans have argued for a long time.