The fire _______ before the fire-fighters arrived

The traffic problems have severely affected economic development ________, we must spare no efforts to solve them

Lily, how do you practice your listening skills—In many ways. Usually I practice them by _____ tapes.

How does Jack usually go to work —He _____ drive a car, but now he _____ there to lose weight.

Will you go to Nanjing by bus _____ by plane—By plane. It is expensive ______ fast.