My mother told the visitors _______ walk quietly and _______ wake the baby up.

In no place other than Britain ____ experience four seasons in a single day.

Although the living standards of Chinese people have greatly improved, most poor families in China spend 50% of their income on food.

One-third of the area _____ covered with trees. About seventy percent of the trees _____ been planted recently.

— Ready to give up, Jim? — No, Hold on! I think I _____to the answer. [ ]