From the question you can immediately infer that it's either B or D, as A and C basically mean the same thing and it isn't anything related to a microscope. I can tell you now that you don't need an electron microscope to see cells, they're only required for the atomic level.
Therefore, the answer is B, as you can't see cells without a microscope but you only need a light microscope, not an electron microscope.
To ensure there safety and comfort of subjects and to make sure the subjects are taken advantage of.
The alkali metal atom forms a +1 ion. the alkaline metal atom forms a +2 ion.
a forms the outer covering of the skin and also lines the body cavity.
