Answer:
The need for continental time zones stemmed directly from the problems of moving passengers and freight over the thousands of miles of rail line that covered North America by the 1880s. Since human beings had first begun keeping track of time, they set their clocks to the local movement of the sun.
Alveoli are part of the reparation system found in the lungs. They are covered in capillaries. In Alveoli, oxygen diffuses from the air into the blood vessels surrounding the alveoli and carbon dioxide from the body diffuses from blood into the alveoli’s air spaces. Alveoli clump together and form sacs.
<span>I believe the answer is: D. proteins
The main functions of these proteins is to allow specific substance to pass through the membrane of the cells which needed for the energy formation for cells'functions.It created through the combination of more than 20 amino acids with different functions.</span><span />
Population because you are holding it
Answer:
Lichens that colonize bare rock secrete acids that break down the rock and start the soil-production process. Also, as lichens die, they provide some organic matter that also contributes to soil. Mosses can then colonize the thin soil; as mosses die, the soil thickens more allowing other hardy species to colonize
Explanation:
