-. How does the author believe that the challenges presented might be solved?

the sphincter muscles at the end of the digestive tract is the anus.

trachea, alveoli, lung capillaries, arteries

he movement of air through earth's or any planet's atmosphere is called wind, and the main cause of earth's winds is uneven heating by the sun. this uneven heating causes changes of atmospheric pressure, and winds blow from regions with high pressure to those with low pressure.

i hope this : )