go on using energy so wastefully, __________ are that our oil wells will be dried up before new energy sources can be found to replace oil.

Could you help me with some math problems–Sure. That’s _______ I’m here.

It is vital that every piece of equipment ________ before the experiment.

Some of the old beliefs passed down from one generation to another ________ the present thinking.

It is well known to us all ____ China sent up a manned spaceship to outer space successfully last year.