Answer:Option A.
Dorsal respiratory group.
Explanation:
Pneumotaxic center is located in the upper part of pons varolli. Pneumatic center help to regulate neuronal activity by inhibiting or limiting the dorsal respiratory group. It sets duration of of inspiration for every respiratory cycle by allowing transitions between inspiration and expiration and limiting the time of inspiration. The maximum inspiration time it can enforce is 40 inspirations per minutes.
Pneumatic center limit dorsal respiratory group .
dorsal respiratory group act as pacemaker of respiratory movements and pneumatic centre limits it.