This is ______ father, Mr Smith.
—What’s electricity?—It’s a form of energy _______ we use in our daily lives.
A student need a ________ place to study, but , in fact, some parents are always watching TV at that time.
When the first settlers came to North America, they had to ________ the forest and found a way out.
—I'd like to go camping with you, but I have meeting _______.—If you don't go, ______.
—Why are the lights in the teachers’ office still on?—There ________ be some teachers working there.