Inspiration is the process that causes air to enter the lungs and expiration is the process that causes air to leave the lungs. If we were to breathe in air our lungs would stretch so we can bring as much air as possible and while expiration makes our lungs unstretch so we can get out as much air as possible so we can get more air into our lungs. Therefore, the answer would be A. Inspiration since it requires the lungs to stretch so we can receive as plenty of air as we need.
