A person who has slept well will have a clear mind and work efficiently in the daytime
______ people with sleep disorders find it difficult to concentrate during the day.
A. unless B. while
C. if D. until
---People often don’t appreciate what they have, do they? ---No, _______ they lose it.
A. if B. after
C. until D. when
It’ll be another 50 years _________ China is expected to reach the level of a medium
developed country.
A. since B. before
C. that D. when
General Secretary, Xi Jinping, stressed that cross－strait cooperation would be strengthened________ the two sides could agree to oppose Taiwan independence．
A． unless B． even if
C． as long as D． until
Mankind must first of all eat, drink, have shelter and clothing ________ it can pursue politics, science, art and religion.
A. until B. unless
C. before D. since
Will it be ages ______ he goes back to school? I'm so worried about him.
A. before B. after
C. when D. as
