The answer to the question given is (A) training to prepare for a career. This is because vocational tends to refer to things that are related to jobs or careers, which makes the other options not appropriate for the definition of a vocational training.
Although one can make a career out of her or his hobby, or improving one’s health, or improving relationships, the options do not state that the purposes of those three trainings are for making income, thus (A) is the best choice.