It was in the lab ______ was taken charge of by Pro. Harris ______ they did the experiment.
I have many friends, _____ some are businessman.
____ is certain, though, is that the mystery of Tutankhamun’s tomb has never been fully explained.
Some time after the rockets and the space shuttle are _____, the rocket will _____ the space shuttle and ____ the sea.
London people always take umbrellas with them, just _______ it rains.
Experts suggest that teenagers spend at least 30 minutes exercising, five times a week. Walking and riding your bike _____ , and ______.