What is the cause of the variations found in different species of living organisms?

Assertion $(S)$: The measure of disorder in a biological system is called free energy.
Reason $(R)$: The energy available in a biological system to perform work is called entropy.
$(A)$ Both $S$ and $R$ are true,and $R$ is the correct explanation of $S$.
$(B)$ Both $S$ and $R$ are true,but $R$ is not the correct explanation of $S$.
$(C)$ $S$ is true and $R$ is false.
$(D)$ $S$ is false and $R$ is true.
$(E)$ Both $S$ and $R$ are false.

Phosphorus is the major constituent of:
$I.$ Biological membranes
$II.$ Nucleic acids
$III.$ Cellular energy
Choose the correct option.

Which of the following vitamins is correctly matched with its solubility and the deficiency disease it causes?

What does the given structural formula represent?

The smallest particle of water is