You should ______ what your parents expect of you.
Does ________ matter much if they do not come tomorrow?
The bell ____ the end of the period rang and we had to stop our discussion
One-third of the area ________ covered with trees. About seventy percent of the trees _______ been planted recently.
Neither Tom nor his parents ________ at home.
--It really shocked us that he should have made such_______ rapid progress in his study in such a short time!--No surprising. He has been making _______ most of his spare time to study.