Final answer:
The recommended administration of feline vaccines to maximize the chance of successful treatment in the event that a vaccine-induced sarcoma develops is proximal to the shoulder or hip in the intrascapular region.
Step-by-step explanation:
The recommended administration of feline vaccines to maximize the chance of successful treatment in the event that a vaccine-induced sarcoma (tumor) develops is proximal to the shoulder or hip in the intrascapular region, which is Option 3. This means that the vaccine should be administered in the area between the shoulder blades on the back of the cat.