I can remember very few ____ when he had to cancel his plans because of poor health．

—Mum, I will leave for tha party. —Remember your     .thank your friend when you leave the party.

We need to work faster because time is _____.

一Tell us, Mark ,what is the ____ of the American Civil War?一 Well, is it because the black slaves wanted freedom?

There seemed to be no human beings in that village, and the only ______ of life was a boat tied to a tree.