Hi Portvale,
Yes, this would stump me. It is true (although rather obvious) that there can only be one sunrise and sunset each day, which is what the preamble to the question says.
The times of sunrise and sunset are given for a range of latitudes in Local Mean Time (LMT) for a particular day. Thus they are correct for all longitudes as LMT, but will need to have the time converted to UTC and possibly Standard Time depending on requirements.
Answer (b) is possibly true if 'these data are accurate only for places on the Greenwich meridian' actually means 'these data are accurate when (incorrectly) read as UTC times only for places on the Greenwich meridian' which is a bit of a stretch involving either a very badly written answer or a serious lack of understanding of LMT and UTC by the examiner.
As the times are LMT they are enough to be used for all longitudes with appropriate corrections applied, and the inference is that they are used to calculate light conditions, (c) is correct.
The sunrise and sunset times are only correct at mean sea level, and adjustment for altitude can be made, (d) is correct.
My money is on answer (a), but for the shabbiness of answer (b) whoever wrote this question should be flogged. Where is it from, please?