Application : the need for homeostasis applies to even one of the smallest living units, cells. The cell membrane controls what goes in and out of the cell. How could the cell membrane then be important for homeostasis?

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

a:

by the combination of an unlimited number of elements