If we don't protect the environment, we will destroy ourselves
If she isn't more hard-working, she will get low marks
If he doesn't listen to his parents, he will fail
They have watched the movie for one hour
He hasn't cried for ten years.
He hasn't gone abroad before
She has driven for one month
We have eaten since it started to rain
Nam is interested in watching TV
I have never talked to the foreigner before