Driving in rush hour traffic __________ be very dangerous, so you __________ be too careful.
—What’s Jim doing?—He ______ a book.
—______ they ______ baseball?—No,they aren't.
—Where are Jeff and Jack?—They _______ in the river.
—Is Paul playing football now? —______.He's playing basketball.
Look!The boys are swimming in the _______.