The bell __ the end of the period rang, __our heated discussion.
At the beginning of the twentieth century,___the population all over the world?
Most environmental problem exist because___measures for preventing them were not taken in the past
He talked happily about the men and the books___interested him greatly in the school
—Do you have anything in mind___you’d like for supper?—Well,___is okay with me
I refuse to accept the blame for something ___was someone else’s fault