Once natural resources _____ , the consequence will beunimaginable.

Is this the first time you ______ Chengdu ? — No. But the first time I ______ here, the city wasn’t so beautiful. [ ]

When I jumped into the river, the water ___very cold

It was from my best friend Jane ________ I learned the truth.

You’d better not wear such ties, because they ____ three years ago.