If he_____his teacher’ s advice, Asafa Powell would not be the fastest man in the world

With the development of science,a computer is to a manager_______a gun is to a soldier

What are you busy with —The conference _______ inour city next week

_and short of breath, Andy and Ruby were the firstto reach the top of Mount Tai

you may have finished unit one. _____ , you can go on to unit two.