Part A
The most fitting inference about Dr. Mesmer's skill would be:
He is aware that his healing force is fake.
This inference suggests that he may recognize that his methods are not based on genuine medical science but rather on manipulation or suggestion, which aligns with the concept of "mesmerism" being more about psychological effects rather than actual healing powers.
Part B
The detail that best supports this inference is:
“He was also experimenting with invisible forces...”
This suggestion of experimentation with forces that are not tangible or scientifically proven implies that Dr. Mesmer might not fully believe in the validity of his methods, reinforcing the idea that he may be aware that his healing force is not real, but rather a fabricated or misunderstood concept.