一般现在时：They play football every day.现在进行时：They are playing football.一般过去时：They played football yesterday.过去完成时：They had played fooball for a week since last week.现在完成时：They have played football since last week.一般将来时：They will/are going to play football tomorrow.过去将来时：They would/were going to play football.
