In much of the animal world, night is the time ______ for sleep—pure and simple.

A society cannot be successful if it throws tradition away，but it cannot be successful ________ if we do something to stop progress.                                

In Disneyland every year, some 800,000 plants are replaced because Disneyland refused to _______ signs asking his “guests” not to step on them.

 Many teachers were impressed by Kris's ________ attitude to life because he never gave up.

.It was so dark in the cinema that I could hardly ________ my friend.