Have you ____ cooked for your parents? —Yes, of course.

You looked unhappy. What’s wrong?—I ________ my PE exam again last week.

Those flowers ________ Kate $56.

Can you tell me to live a low-carbon(低碳) life? — OK. Use both sides of the paper. Don’t use plastic bags or disposable goods(一次性用品).

The zoo keeper is worried because the number of visitors ______ smaller and smaller .