Read the following article and select the best answer.
Article: While the rest of the world carried on cycling during the 1950s and 1960s , America forgot how ; even high-school children would drive to school . Recently there has been something of a recovery in cycling , and in many areas it is a very useful way of getting around , especially where bike paths or bike routes have been built . You may well want to buy , hire or borrow a bike .
There are two important results of this earlier drop in cycling in the USA . One is that many people do not know how to cycle . That is , cyclists often behave more like walkers than motorists : they ride in the sidewalk or on the wrong side of the road ; they do not care for stop signs or traffic lights ; they ride without lights at night ; they give no signals .
The other result is that cycling is regarded by many people not so much as a way of getting from one place to another but as a way of life , a form of exercise , etc . As a result , large numbers of young Americans have ten-speed racing bikes . These are very high and fast and great if you are cycling long distance , riding up mountains or racing . At first , though , you may find them convenient for cycling in town , sightseeing or shopping --they are expensive , uncomfortable and hard to control until you get used to them , and unsuitable for rough stony roads .
There are also ordinary bikes around . If you get hold of one of these ,you may find that the brakes  work by pedaling   backwards . This is perhaps safer than ordinary brakes when it is wet , but it seems to be less effective . This arrangement also means you can't pedal backwards in order to get the pedal in the right place for getting on or getting off .
Question: Young Americans prefer racing bikes because they   _  .
- can help keep fit
- are easy to learn
- are safer to ride
- are expensive and popular
can help keep fit
This article talks about the revival of cycling in America and its impact on people.
The first paragraph mentions that many Americans have started to cycle again due to more bike paths being made available for cyclists, which indicates a rise in bicycle usage among American citizens. 
In addition, it states that young Americans prefer ten-speed racing bikes because they are faster and safer when used over long distances or up mountains but can be expensive until you get accustomed to them. Ten-Speed Racing Bikes is also known as Road Bike Cycling which requires riders to go through extensive training - similar to marathon running - making this activity an excellent way to keep fit so the answer could either be "can help keep fit" or "are expensive and popular".


However, given all other information provided by the author.