Translation:The tourists were exiting the train for five or six minutes.
Should allow exiting "from" the train. US English often omits words like this, whereas UK English requires them. Another example is where in the US, you protest something, but in UK English you must us protest "for" or "against". It's also marked as transitive/intransitive too. So, as an intransitive verb, you must use "from".
I have added alternatives that include "from," as Oxford Living Dictionaries supports it: https://en.oxforddictionaries.com/definition/exit. Sample sentence similar to the one in this exercise: "‘While I was waiting at the arrivals gate, a large group of people exited from the flight previous to the one I was waiting for.’"
This is a horrible translation into GBEng. To exit is not a natural conversational word for getting off trains. It's very official. If this is a police report, I will reluctantly support it. However, if you are explaining to your girlfriend why you are late, you would say, 'Those tourists were taking five or six minutes getting off the train.' The translation of the imperfective aspect is what is important.