On reflection, the LMT times of sunrise and sunset will change from day to day, and therefore with the rotation of the earth. The LMT of sunrise at a particular latitude and 179deg59'W might be read from the almanac as 0600 LMT on the 5th March, for instance (made up numbers), whereas the LMT of sunrise from the tables for the next day at the same latitude and 179deg59E (only a few miles away) might show as 0605. Clearly they cannot both be correct, and in fact neither is, because the tables show LMT of sunrise and sunset at greenwich on the assumption that the difference for up to 12 hours equivalent of longitude is not wildly significant. That might be a better reason why (b) is true and avoids me slandering the examiner.