20.You have to have a good preparation for the exam__________ you can do well in it.
There was a __________look on her face because a________ problem _________the little girl.
His first concert was well ____ and so all the tickets of his second one were sold out quickly.
The experts advise _______ our army _______ modern weapons.
This dictionary is at least three times as thick as you borrowed from the library.
He _______ have completed his work;otherwise, he wouldn’t be enjoying himself by the seaside.