Ineed !
(1) experts have several theories to explain why people yawn. (2)one explanation is that yawns boost oxygen levels in the blood. (3)by forcing the body to breathe deeply, yawns increase airflow to the lungs and rush oxygen to the bloodstream. (4)a second theory is that yawns the body change its level of alertness. (5)it is for this reason yawns happen whether a person is waking up or getting sleepy. (6)yet another explanation is that yawns, like stretches, give the body exercise. (7)when a person yawns, blood pressure and heart rate gently increase and muscles flex. (8)no matter what the cause for yawning, one thing is clear. (9)fifty-five percent of the people who read this paragraph will yawn in less than five minutes.

7. the passage contains

a. three major supporting details.

b. four major supporting details.

c. five major supporting details.