Answer:
21
Explanation:
Amino acids are the basic structural units of proteins. Our bodies contain 21 amino acids it uses to make all proteins, although books recognize only 20 amino acids. The 20 amino acids are the alphabet of proteins.
The answer is A. Oligotrophic lakes are clear and hence
have little vegetation in them (hence no net primary production) that
could initiate the process of eutrophication. Eutrophication is brought about when bacteria
break down the high amount of organic matter hence reduce the oxygen supply in
the waters.
Thus, if the cell grows beyond a certain limit, not enough material will be able
to cross the membrane fast enough to accommodate the increased cellular
volume. When this happens, the cell must divide into smaller cells with
favorable surface area/volume ratios, or cease to function.