Final answer:
Walking is not controlled by the autonomic nervous system, which instead regulates involuntary functions like digestion, heartbeat, and temperature regulation. Walking is a voluntary action controlled by the somatic nervous system.
Step-by-step explanation:
The function not controlled by the autonomic nervous system (ANS) is B. walking. The autonomic nervous system manages various involuntary physiological functions, such as digestion (A), heartbeat (C), and temperature regulation (D). These processes occur without conscious thought. Walking, on the other hand, is primarily a voluntary action that involves the somatic nervous system, which controls the movement of skeletal muscles. While the ANS can modify the blood flow to muscles during walking, the actual control of the motor movements involved in walking is not an autonomic function.