The answer is c. the others are compounds.
Answer: A, Nucleus
B, Cell memebrane
C, vacuole
D, Chloroplast, mitocondria, amyloplast.
Explanation:
These only work if this is a plant cell which you did not specify.
There are 8 valence electrons in the Kr atom, this is because Krypton is in the 8th group. Krypton is in the far right row of the periodic table, making it the outermost shell (which is 8 valence electrons)
Hope this helps!
(2) Adding more O2(g) would shift the equilibrium to the right because a higher concentration of oxygen is offered than its initial position, therefore more products have to be yielded to maintain equilibrium.
