Since 1949, the people’s living standard _______, causing a big _______ in population.

Many people can’t learn lessons from the mistakes they’ve made_____they get hurt somehow.

I _____ her voice at once on the phone, though we hadn’t seen each other for ten years.

he is very poor, he feels very happy.

If you have trouble pronouncing these words, you can repeat them over and over again ________ you are comfortable with them．