The first use of atomic weapons was in 1945, and their power ________ increased enormously ever since.
Lots of waste has been dumped into the river,which has led to________.
There was a________ look on his face when he met with the________ problem.
You’d better go there by train. The train ticket is________ the airplane ticket.
—Shall I give you a ride as you live so far away?—Thank you,________.
At times the balance in nature is____, resulting in a number of possibly unforeseen effects.