—Who taught ________ to write the computer program?—Nobody. She learned it by __________.
—What a nice bicycle! How long have you _____ it ? —For a week.
—In the old days, most teenagers had to work for the landlord (地主) in the field to help _____ their families, because their families couldn’t _____ education for them. —What a pity!
In our class _____ of the students _____ girls.
—Which country has the_____population in the world? —China.
—David has made great progress recently. —_____, and _____.