I believe (not sure) that the answer is B, viruses must invade their host before being able to reproduce.
I remember seeing a diagram of the general life of a virus, and I remember seeing the virus sticking to a cell, merging in, and reproducing thereafter (sort of like a factory). Once again, I am not sure and the answer may as well be another one.
If the side of the triangle is ' S ', then . . .
-- Base of the triangle = S
-- Height of the triangle = 1/2 S √3
-- Area = 1/2 (base) (height) = (S² √3) / 4
-- Perimeter = 3 S
Area / Perimeter (numerical) = [ (S² √3) / 4 ] / 3 S
That ugly thing becomes <em>S √3 / 12 </em> .
The answer is: [D]: "molecules" .
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The fluid-mosaic model describes the plasma membrane of
animal cells. The plasma membrane that surrounds these cells has two
layers (a bilayer) of phospholipids (fats with phosphorous
attached), which at body temperature are like vegetable oil (fluid).
And the structure of the plasma membrane supports the old saying, “Oil
and water don’t mix.”
Each phospholipid molecule has a head that is attracted to water (hydrophilic: hydro = water; philic = loving) and a tail that repels water (hydrophobic: hydro = water; phobic
= fearing). Both layers of the plasma membrane have the hydrophilic
heads pointing toward the outside; the hydrophobic tails form the inside
of the bilayer.
Because cells reside in a watery solution (extracellular
fluid), and they contain a watery solution inside of them (cytoplasm),
the plasma membrane forms a circle around each cell so that the
water-loving heads are in contact with the fluid, and the water-fearing
tails are protected on the inside.
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