Assertion (A): An iron ball floats on mercury but gets immersed in water. Reason (R): The specific gravity of iron is more than that of mercury.

The correct answer is C because the Assertion is true but the Reason is false. According to the principle of flotation, an object will float in a liquid if its density is lower than the density of the liquid and sink if its density is higher. The density of iron is approximately 7.8 grams per cubic centimeter. The density of water is 1.0 gram per cubic centimeter, while the density of mercury is much higher at approximately 13.6 grams per cubic centimeter. Since iron is denser than water, it sinks in water. However, since iron is less dense than mercury, it floats on mercury. Therefore, the Assertion is true. The Reason is false because it states the opposite of the physical reality. The specific gravity of iron is actually much less than that of mercury, which is precisely why it is able to float on it.