Question

Which matter is left uncertain in this excerpt?%0D%0A%0D%0A(1 point)%0D%0AResponses%0D%0A%0D%0Athe idea that yawns involve the muscles of the face%0D%0Athe idea that yawns involve the muscles of the face%0D%0A%0D%0Athe chemicals that make up “yawn gates”%0D%0Athe chemicals that make up “yawn gates”%0D%0A%0D%0Athe exact scientific reason for yawning%0D%0Athe exact scientific reason for yawning%0D%0A%0D%0Athe 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**.