Thanks for the question! (A) is about declining PROFESSIONAL positions for NONPROFESSIONAL ones. So a professional position is generally considered to be something like a lawyer or engineer, and a nonprofessional one might be like a grocery store worker. (B), on the other hand, is about PART-TIME vs FULL-TIME employment. Note that you could have a part-time job be professional or nonprofessional, and it’s certainly possible to have a full-time job be either.
Hope this helps! Feel free to ask any other questions that you might have.
