—Why do you look sad?—There are so many problems ________.
It even leaves the scientists in _______what they should call the newly born creature, which looks half-human and half-animal.
Doctor Lily has made her projects successful, so we suggest not only _______ to her old school but also give the students a talk then.
I don’t have money or time in hand; _____, I can’t accompany you to the Parkson Mall today.
In order to keep the balance of ecosystem, every possible means _______to deal with the problems of the over-exploiting of natural resources.
We all thought that Betty could have run _______ if she had worn the sports-shoes that day.