----_____is it that is troubling Mary ?----Working out the maths problem..
Rather than ______ his own car work, he preferred ______ public transport.
The terrible shaking of the building woke up all the people _______ were asleep.
You should always exercise, ______ it’s only ten minutes every day.
____ large number of children have joined the book club and ____ number is increasing.
I don’t ______ the price, as long as the house is in good condition.