Answer:
Cell membranes
Explanation:
Cell membranes is a feature that is common to prokaryotic and eukaryotic cells.
Rainwater is fairly pure
however it can also pick up some particulate matter and electrolytes from the
air, although not much. It will be saturated with atmospheric CO2, so with a little
buffering capacity, it will be at a pH of about 5.5, which is also the pH of
carbonic acid, a weak acid. Hence rainwater is a weak acid.
The energy of an electron can be change only by set amounts.
The electrons in an energy level of an atom can only move to a higher or lower energy level only if it absorbs or emits a certain amount of energy. If the electron does not have enough energy to move to the next energy level then it will never move.
Reduction. B is the correct answer