I ______ go to bed until I ______ finished my work. a. don’t/had b. didn’t/have c. didn’t/had d. don’t/have
6.Newly-developed materials for spaceships can___________extreme weather conditions.
5.A good teacher is ________who is always doing things for the good of the students.
4.The first time I met David in the Central Park, both of us felt that we________each other for ages.
3.---How much do I owe you for this beautiful vase? ---____.It’s a gift.
2.Despite the fact that Betty is a lovely girl, she___________be extremely difficult to work with sometimes.