"At constant pressure, the volume of gas is directly proportional to Absolute Temperature". This is known as:

Explanation

Charles's law, discovered by Jacques Charles, states that for a fixed amount of gas at constant pressure, the volume is directly proportional to its absolute temperature (measured in Kelvin). This is the correct answer because the question describes this exact relationship. Boyle's law is incorrect because it deals with pressure and volume at constant temperature. An isothermal process is irrelevant here as it involves constant temperature, not constant pressure. The general gas law (ideal gas law) is a broader equation that includes multiple variables but does not specifically define the relationship asked about. Henry's law is unrelated to volume and temperature; it involves the solubility of gases in liquids.