It is no ________ arguing with Bill because he will never change his mind.(全国高考)
His test results are not very _____. He does well one week and badly the next.
Scientists think they have _____ in their attempt to find the causes of some major dieases.
If you ever have the _____ to go abroad to work, you should take it.
Stressful environments lead to unhealthy behaviors such as poor eating habits, which _____ increase the risk of heart disease.
Teenagers their health because they play computer games too much.