As is often pointed out, knowledge is a two-edged weapon which can be used ________ for good or evil.
doesn’t seem to have been much difficulty in solving the problem.
A recent survey shows ____ great social changes, traditional values like family harmony still play an important role in Chinese people in heart.
— Did Peter fix the computer himself? — He ________, because he doesn't know much about computers.
Without my glasses, I couldn’t _______ whether that figure on the blackboard was a three or an eight.
Dogs have a very good ___________ of smell and are often used to search for survivors in an earthquake.