Assertion: Water at 100 °C causes more severe burns than steam at 100 °C.

Reason: Steam has the highest specific latent heat of vaporization.

The correct option is D

‘A’ is incorrect, but ‘R’ is correct

The explanation for the assertion:

1. Steam at 100 °C causes more severe burns than water at 100 °C because water absorbs latent heat of vaporization from the surroundings to convert into steam at a constant temperature.
2. So, even though its temperature is constant, because of the high amount of heat, steam is hotter than water at 100 °C

The explanation for the reason:

1. The specific latent heat of vaporization of steam is the amount of heat energy required to change the unit mass of water at 100 °C into steam at 100 °C.
2. Its value is 226 x 10⁴ J kg^-1.
3. Steam has the highest value of the specific latent heat of vaporization.

Hence, the correct answer is (D) ‘A’ is incorrect, but ‘R’ is correct.