This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
As you pull down the balloon at the bottom of the lung model, the small balloons inside it will expand, thus, the air comes inside the balloons.
3 4 3
The model will react on it :)
2 4 2