At times the balance in nature is ______ , resulting in a number of possibly unforeseen effects.
John received an invitation to dinner, and with his work ________, he gladly accepted it.
He was educated at the local high school, ______ he went on to Beijing University.
—Ouch! You hurt me! —I am sorry. But Iany harm. Ito drive a rat out.
He didn’t make __________ clear when and where the meeting would be held.
Dogs have a very good ___________ of smell and are often used to search for survivors in an earthquake.