Xi’an was attacked by such a terrible smog _____ few residents had ever experienced before.
A good teacher should leave some time for the students to _________ the knowledge.
There is no doubt that a small child has to learn to keep its _________ before it can walk far.
The reason why Daisy eats so little is that she is _________ a diet and she is trying to _______ weight.
-Hello, Mr. Wang. Must we wear the school uniform tomorrow?-You ___________. Only on Mondays. Tomorrow is Tuesday.
The Curies were ___________ the Nobel Prize for their great contributions to science.