Scientists have found no ________of life on Mars so far,though great efforts have made on the research.

Finding information in today’s world is easy. The ______ is how you can tell if the information you get is useful or not.

Do you have any ________on forbidding drunk driving ?

One of the advantages of living on the top floor of a high rise is that you can get a good ____.

Before building a house, you have to ask for the government’s _______.