Answer:
Lung function tests (also called pulmonary function tests) include a variety of tests that check how well the lungs work. The most basic test is spirometry. This test measures the amount of air the lungs can hold. The test also measures how forcefully one can empty air from the lungs.
External stimulus. The rain is something out of your control while you're waiting. Rain is not something you are doing nor is it a response to you waiting for the bus.
