ANS:C - both(a)&(b)

The heat of reaction, also known as enthalpy change, is primarily a function of temperature. Changes in temperature directly affect the heat of reaction, as they alter the energy levels and interactions between the reactant molecules, thus influencing the energy released or absorbed during the reaction. Pressure, on the other hand, typically has a negligible effect on the heat of reaction under standard conditions (ambient pressure). However, at very high pressures or for reactions involving gases, pressure effects may become significant. Nonetheless, pressure is generally not considered a primary factor influencing the heat of reaction compared to temperature. So, the correct answer is "temperature".