B. Effector
Effector is the correct answer. In this scenario, Jenny's body is sweating to maintain homeostasis. Sweating is the response or action of the effector organs (sweat glands) to maintain the body's internal temperature within a narrow, optimal range. The effector organs respond to the signals sent by the control center (usually the brain or spinal cord) in response to information detected by sensors in the body. In this case, the sensors are detecting an increase in body temperature due to exercise and sending signals to the brain, which in turn sends signals to the sweat glands to produce sweat and cool down the body.