---How long did it _____ you to work out the difficult maths problems?---I ______ about half an hour on it .
The baby is about 52 centimeters tall________birth.
—________the population of China?—It’s about 1.3 billion.
—What do you think of the film you saw yesterday?—Oh!It’s one of________films I’ve ever seen.
Who listens________,Tom,Jack or Bill?
—It’s one of the________things in the world to stay with friends.—I agree.It always makes us relaxed.