Given below are two statements, one labelled as Assertion A and the other labelled as Reason R. In the light of the above statements, choose the most appropriate answer from the options given below.

Eutrophication does lower dissolved oxygen and warmer water does hold less oxygen, yet the second point is not the real reason for the first.

Nutrient overload triggers algal blooms that later die and decay.

Decomposing this dead matter consumes large amounts of dissolved oxygen, the true cause of the oxygen loss.

The reason notes that oxygen solubility falls as temperature rises, which is separately true.

Since decay rather than warming drives the oxygen drop in eutrophication, the reason does not explain the assertion.

This oxygen starvation can create dead zones where fish and other life cannot survive.