Final answer:
a) Smooth muscles are less active than skeletal muscles, while smooth muscles, which are controlled by the autonomic nervous system and active in maintaining vital body functions, are not as affected by inactivity.
Step-by-step explanation:
a) Smooth muscles are less active than skeletal muscles. The difference in the response of skeletal muscles and smooth muscles to a sedentary lifestyle lies in their inherent characteristics and functions. Skeletal muscles, which are responsible for voluntary movements, experience atrophy when not regularly engaged in physical activity. The lack of exercise leads to a reduction in muscle mass and strength. In contrast, smooth muscles, found in organs like the digestive tract and blood vessels, perform involuntary functions and are less directly influenced by conscious physical activity. They are continuously active to maintain organ function, and their structure is less prone to atrophy in response to a sedentary lifestyle compared to skeletal muscles.