When changing lanes, a driver should use his turning signal to let other drivers know ______.
. All her time _______ experiments, she has no time for films.
. He knows nothing about it, so he can’t help _______ any of your work.
He ran as fast as he could _____ to catch the early bus.
. Everyone in our class was working hard and doing what we could _______ a good college.
. You should ______ what your parents expect of you.