As their memories decline, some old people tend to be talkative because they ______ forget what has just been said.

The rapidly growing birth rate brings about a lot of environment problems, which the government is supposed to take _____.

The question is _____easy, so everyone in our class can answer it.

He was beaten by his father because of being naughty. ____, he became silent.

Wang Ping hesitated for ___ before he ___ to the question.