In summer milk will quickly go bad_____ it is put into a fridge.
—_____will you stay here? —Until tomorrow afternoon.
My shoes are worn out.They need_______.
He hadn’t worked hard at his lessons._______, he failed in the exam.
— When did the meeting begin?—At four o’clock.It ______ for 15 minutes.
It is said that the gravity on Mars is only about __________ of the gravity on earth.