The only question you should ask a personal trainer is whether or not they are certified.

One should hire a certified personal trainer to avoid getting wrong training and to getting hurt.

A personal trainer sets fitness goals, advises  on fitness, diet, nutrition and life style , helps in workouts and monitors the progress of their clients according to their fitness level.

To guide the clients in a proper way a personal trainer should possess certain certified degrees like- diploma in Gym Instructing, Diploma in Health and Fitness instruction, and diploma in Personal Training etc.

Though many personal trainers are not certified to be one and continue to work without any professional certificate. However, one should always hire a trained and certified personal trainer to have a proper training without any mishaps.  

i think the answer would be b.