Exercise 2 solution

This depends on your own photographs, so there is no single answer. A good answer records for each picture: subject on a line / on an intersection / near centre, and an honest judgement.
The point of the exercise is to compare. The article calls the rule a rule of thumb; George Field (1845) argued it is neither accurate nor universal, and a 2014 study reported it plays only a minor role in high-quality images. A centred picture can work well, for example a symmetrical one. Giving a specific reason (subject, balance, space in front of a moving subject) is better than saying "it looks better".