Final answer:
Professional speakers inhale deeply before beginning their speech to enhance lung capacity.
Step-by-step explanation:
When a professional speaker inhales deeply before beginning their speech, they are enhancing lung capacity.
Inhalation in humans and other mammals involves expanding the thoracic cavity by creating negative pressure in the lungs, which causes air to diffuse into the lungs.
By taking a deep breath, professional speakers are increasing their lung capacity, allowing them to have more air stored in their lungs. This can help them project their voice louder and speak for longer periods without getting out of breath.