A、Basketball. B、Football. C、Baseball. D、Golf. C短文提到，棒球运动是美国全国性的娱乐活动，C正确。

Professional sports are very popular in the United States,and they are big business.The most popular sports are baseball,football and basketball.Each has its own season,and millions of supporters.Professional teams are named after the cities where they are located Their strongest supporters live in these cities When a team plays in a championship game,most people in the city follow the game with interest and enthusiasm.Basketball is well known around the world.Professioal basketball games in the United States are played indoors during the winter months. From November to April one can find a professional basketball game several nights a week in most large American cities.Baseball is an American sport.It has been called the national pastime.The game is played in the evenings nearly every day of the week and on weekends as well.The season begins in April and finishes with the World Series in October.Football has become the most popular professional sport in the U.S.It is played on Sundays during the fall from August to January.American football is different from interational football,which Americans call soccer.Both games require strength and specialized skills. Professional athletes are very well paid.The most famous athletes make millions of dollars for their playing skill. America’S best athfetes have higher salaries than the country’s president.