Use the excerpt to answer the question. Which matter is left uncertain in this excerpt? (1 point) Responses the idea that yawns involve the muscles of the face the idea that yawns involve the muscles of the face the chemicals that make up “yawn gates” the chemicals that make up “yawn gates” the exact scientific reason for yawning the exact scientific reason for yawning the reason that yawns are a special kind of respiration

Answer 1

The matter that is left uncertain in the excerpt is "the exact scientific reason for yawning."