Walk ______ the house, and you’ll see a big tree on your left.
-Why have you decided on the countryside for your holiday? -Because we are there is lots of clear, fresh air there.
Every minute about ____ babies are born in the world, so the world’s population is increasing by _____million every year.
Acid rain comes from _____.
Many _____ in ______ could hear no better than 65-year-old people, for they like pop music.
Mr. and Mrs. Green work in the hospital, but they have no children. So they belong to _____.