My neighbor is very kind. I’ll never forget the ______ she’s done for me.

The old man kept on studying Chairman Mao’s ___ in his ___.

The ______ has become extremely tense. A war could break out any time between the two sides.

Peter will come to understand your efforts sooner or later. It’s just a matter of _____.

There has been a（n）____of sadness in the small town since a boy was drowned in the river．