A、You can sleep in it. B、it’s safer than trains. C、It’s fast and comfortable. D、You can see more of the country. D细节题。短文第二句就提到Th

Although America is a huge country, traveling is very quick and easy. The visitor who wants to see as much of the country as possible should travel by bus. That is, if he hasn’t got a friend who owns a car. It’s fun. There is fast bus service between cities. For example, the Greyhound bus service has the picture of a greyhound, a dog which can run very fast on the side of the bus. Some buses have an upper and a lower level. The roof is often made of glass and in the summer the heat of the sun through the glass makes it feel too hot. Although the buses are cooled by air conditioning, it does not always seem to work with such good effect on the top level. The seats are soft with a reading lamp over each one and they lean back for sleeping at night. On these long distance buses there is a toilet and other comfort on board.
    Stops are made for meals at roadside restaurants and there is time to stretch your legs. It takes about three and a half days to cross America by bus with short stops for meals.
    Flying is as simple as going by bus. There are two kinds of service: a regular service on which free meals are provided, and a stop over service where the plane stops over at various cities. Most cities have an airport. You can often buy your ticket and arrange your airplane trip all within about twenty minutes. Businessmen who are in a hurry do all their traveling by plane. The roads and highways are splendid, running straight for hundreds of miles. Some are free ways which means that there is no charge for using them or others called turnpikes the drivers have to pay.
There are no crossroad or traffic lights. Other roads run either above or underneath the highways with roads leading up or down to them from either side.