Answer:
a is perpendicular to c will be the answer.
The parasympathetic nervous system <span>conserves energy as it slows down heart rate, increases intestinal and glandular activity, and relaxes the sphincter muscles of the gastrointestinal tract. It gets the nickname "rest and digest" for doing exactly so. Typically most active when sleeping, however is also the explanation for post-prandial fatigue, or being tired after eating (especially a large meal).</span>
Carbon dioxide is a byproduct of respiration while oxygen is a byproduct of photosynthesis.
Remember that a byproduct is a secondary product that is made in the synthesis of another. It is unintended and excreted.