The correct option is D Assertion is incorrect but Reason is correct
An intermediate is relatively high-energy species that has some short but finite life time duration during the course of a reaction. Intermediate reside in a local free energy minimum on the reaction co ordinate-not a maximum.
Activated complex" is a word used to describe the reacting molecules in the transition state. The activated complex is at the top of the energy barrier. Hence, they are not same.
It is elevated to a higher quantized vibrational state i.e., it is unstable with high vibrational energy.