---Where is my pen?--- I _____it.

—Are you coming to Jeff's party?—I'm not sure.I ________ go to the concert instead.

–– ________ I come back before 6 o’clock?–– No, you _______ . But you ______ be back later than 7 o’clock.

--May I pick a flower in the garden? --No, you _________.

Cars play an important role in modern life, but they ______ also cause many problems like air pollution.