Suggest you clarify the "take a bus" instruction. Does it mean taking a bus to train is not a train service (i.e. a correct answer), or does it mean taking a bus to train does not count as a correct answer? I think you intend the former. If so, suggest you make it read "that is considered an airport WITHOUT train service".
The former. But I clarified a bit. So, for example, at JFK and Newark you have to take an AirTrain to get to the actual train. Those count as airports with train service. But at LAX and Boston, you have to exit the terminal, get on a shuttle bus that takes you partway into the city, and then you can get on the train. Those do not count as airports with train service.