It says the correct answer is 'An oíche'. Which is wrong, it means 'the night'. The correct answer should be 'an tráthnóna,
That's fair enough, although I have never heard it used in that form. But my point is that within the Dates/Time lesson it does not tell you that it can be used for both, it simply states that 'tráthnóna' is 'evening' and 'oíche' is 'night'. Therefore the lesson should be altered to include 'oíche' in the explanation of 'evening', or they should leave it as is but amend the above question.