, all the quarrels came to an end.

With sufficient scientific information a manned trip to Mars should be _____.

Peter, don’t play that kind of jokes any more–Sorry, I ________ do it again.

They felt ________ it was high tax and low income ________ contributed to the extreme misery of the working people at the bottom of the ladder

Polar explorers have to be extremely _____ to bear the climate and other hardships.