Given below are two statements: one is labelled as Assertion (A)...

The absolute pressure $P$ at a depth $h$ is given by $P = P_{atm} + \rho g h$.

For a quantity to be directly proportional to another, their relationship must be of the form $y = kx$ (a straight line passing through the origin).

Because of the presence of the atmospheric pressure term ($P_{atm}$), which is a non-zero constant, the relationship between $P$ and $h$ is linear but not directly proportional. The graph of $P$ versus $h$ has a positive y-intercept.

Therefore, the Assertion is true. The Reason correctly identifies that the absolute pressure includes this non-zero constant (atmospheric pressure) alongside the gauge pressure ($\rho g h$), which perfectly explains why the relationship is not a direct proportionality. Thus, the Reason is true and is the correct explanation of the Assertion.

Answer: Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)