Look at that little boy wandering about — perhaps he _____ his mother.
The engine just won't start.Something seems ________ wrong with it.
It's no use ________ without taking any action.
No matter how bright a talker you are, there are times when it's better ________ silent.
________basic firstaid techniques will help you respond quickly to emergencies.
If he takes on this work, he will have no choice but ________ an even greater challenge.