All the information is answered/given in the paragraph except that the study doesn’t show cells in their natural habitat!
Answer: The blood circulatory system (cardiovascular system) delivers nutrients and oxygen to all cells in the body.
Explanation:
The answer is B.
occur gradually over millions of years.
A molecular formula represents the exact number of atoms present for each element in the compound.
For carbon atom:
=
( as molar mass of carbon is 12 g/mol)
Now, 6 carbon atoms are present and rest are hydrogen atoms i.e. 6
Thus, formula becomes
(
Now, check for unsaturation:
Degree of unsaturation = 
Substitute the value of x and y,
Degree of unsaturation = 
= 
=
implies one ring and three double bonds.
Thus, formula comes out to be
i.e. benzene ring.