如果你用卡来支付车费 你可以免费从公交换乘地铁 两小时之内地铁转公交或者公交转公交你支付车费 最后一句语法有问题 前两句应该是对的
IF you pay your fare with a card,you may change free from bus to subway,subway to or bus to bus within two hours of the time you paid your fare.
如果你用交通卡付费,你可以在付费后两个小时内,免费由公交转乘地铁,或由地铁转成公交