Do remember to be ________. We must avoid any possible risks when doing this dangerous chemical experiment—burns, poisonous gases or cuts from broken tubes.
Plastic bottles can be recycled but they need cleaning thoroughly, _______ they?
Of all the methods they provided, ______ is of any help for solving the math problem.
—Tom seems to be familiar with London. ---Yes. He ___________ here for three years. It’s great for him to be back.
A modern city has been built _____ a very small village was many years ago.
---There’s someone knocking on the door. Who _________ it be? ---It must be John. He promised to be here at 8:00.