Some birds fly in winter and some stay in the north.
Chemical pollution will bring about a threat to agriculture and food chain, andto human health.
By the year of 2053 there will be 487 million aged people in China, means that one third of the population will be over 60.
It is hoped that one day all the wild animals shut up in the cages will be set free to nature and live happily in wild.
Don’t be discouraged. ____things as they are and you will enjoy every day of your life.
She hurriedly left the room without saying anything as if ____.