The dolphins ____________interesting in the zoo.

A kind of little cars may take the place of today’s big ones many years later. If everyone drives such cars in the future, there will be less pollution in the air. There will also be more space for parking in cities, and the streets will be less crowded.

The little cars of the future will cost less. Driving will be safer, too, since these little cars can go only 65 kilometers an hour. The cars of the future will be fine for going around a city, but they will not be useful for a long way. Little cars will go 450 kilometers before they need to stop for more gasoline (汽油). If big cars are still used with the small ones, two kinds of roads will be needed in the future. Some roads will be needed for the big, faster cars and other roads will be needed for the small, slower ones.

1..There is much pollution in the air today because _____.

2..The usual size of cars today is _____.

3..Two kinds of roads will be needed in the future because _____.

My work is ________ dangerous.

French is _______ difficult to learn.