--__________must be working in the office, I think. --Sure, the light is still on.

Use your head; nothing taught by others can have the same effect on you as _________learnedthrough practice.

All 　　is needed is a supply of oil.

At______ time does the salesgirl get up late in the morning.She is too busy to take a good rest.

They often change the kind of crop in each field ____ few years, for example, growing corn or wheat and then the next year peas or soybeans.