Resonance energy is the difference in energy between the actual compound and its most stable resonance structure. It can be calculated by subtracting the heat of hydrogenation of the compound from the heat of hydrogenation of the hypothetical compound in which all the double bonds are converted to single bonds.

To understand why the correct answer is option D, let's analyze the heat of hydrogenation for both cyclohexene and benzene.

1. Heat of Hydrogenation of Cyclohexene:
The heat of hydrogenation of cyclohexene is given as 119.5 kcal. This value represents the amount of heat released when one mole of cyclohexene is converted into cyclohexane by adding hydrogen. This process involves breaking the double bond and forming two new single bonds.

2. Heat of Hydrogenation of Benzene:
The heat of hydrogenation of benzene is given as 248 kcal. This value represents the amount of heat released when one mole of benzene is converted into cyclohexane by adding hydrogen. However, benzene is a highly stable compound, and its heat of hydrogenation is less than the expected heat of hydrogenation for a compound with three double bonds (3 × 119.5 kcal = 358.5 kcal). This lower heat of hydrogenation indicates that benzene is more stable than a compound with three isolated double bonds.

3. Calculation of Resonance Energy:
To calculate the resonance energy, we need to compare the heat of hydrogenation of benzene with the expected heat of hydrogenation for a compound with three isolated double bonds (358.5 kcal).

Resonance energy = Expected heat of hydrogenation - Actual heat of hydrogenation
= 358.5 kcal - 248 kcal
= 110.5 kcal

Therefore, the correct answer is option D, 110.5 kcal. This value represents the resonance energy, which is the difference in energy between the actual compound (benzene) and its most stable resonance structure.