Question

why does the author say yawning is contagious? people like to do research on yawns. people stretch and yawn at the same time. people yawn after seeing others yawn. people pretend to yawn with their friends.

Explanation:

To determine why yawning is contagious, we analyze each option:

• "People like to do research on yawns" is about research interest, not why yawning is contagious.
• "People stretch and yawn at the same time" describes a co - occurrence of actions, not the contagious nature of yawning.
• "People yawn after seeing others yawn" aligns with the definition of contagious yawning, as one person's yawn triggers another's.
• "People pretend to yawn with their friends" implies a voluntary pretense, not the involuntary contagious response.

Answer:

C. People yawn after seeing others yawn.