[多项选择]美国所有较大的城市几乎都有职业橄榄球队，其运动员大多数是原来的大学橄榄球运动员。通常，职业橄榄球比赛的观众人数比大学橄榄球比赛的还要多，这是因为职业运动员势必要艺高技胜一筹。大学橄榄球比赛通常在星期六下午进行，而职业橄榄球比赛常常在星期日的下午或晚上举行。

参考答案:
The American football sport, originating from the English soccer, is absolutely different from the usual match, the soccer sport. In the autumn, football is the most popular sport in American colleges and middle schools. Colleges often encourage the excellent high school football players to enter by offering them scholarship and free accommodation. Football matches are very popular, so colleges often can use the tickets earning to afford other sports expenses.
Nearly all the bigger cities in America have a professional football team, in which most of the team members are the college players. Usually, the number of spectators of a professional match is far more than that of a college football match, which because the professional players are certainly more skillful. College football matches are usually held on Saturday afternoons, while the profession- al ones are often held on Sunday afternoons or in the Sunday evenings.