Some scientists believe that it won’t be long _______ robots are widely used in all walks of life．
A． since B． after C． before D． until
Under no circumstances _______ the difficulties when they were on an expedition to the Antarctic．
A． they gave way to B． did they give way to
C． they had given way to D． had they given way to
In the city, I saw so grand a National Day celebration _______ I never dreamed of．
A． which B． as C． that D． when
If only I _______ more confidence in the English speech contest held last week!
A． would have B． had C． had had D． have
According to the school rules, no child _______ be allowed out of the school during the day, unless accompanied by an adult．
A． will B． would C． might D． shall
It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it．
A． when; which B． when; that C． that; which D． that; that
