When the diaphragm and external intercostal muscles contract, it

The correct answer is: lets the air get inside the lungs.

Explanation:

The process of ventilation, or breathing, consists of two parts: inhaling and exhaling.

Inhaling is the name of the process that is responsible for the air entering the body by the respiratory tract. Exhaling is the opposite, it lets the air out. Both are equally important since they allow the gas exchange necessary for the oxygenation of the blood.

When inhaling, the diaphragm and the external intercostal muscles contract. This pulls the ribcage upwards and outwards, which increases lung volume while decreasing the air pressure inside.

the sphincter muscles at the end of the digestive tract is the anus.

i think the answer would be d