Computational quantum chemistry is widely used in the study of possible reaction pathways along with the intermediates and transition states. Which of the following statements is not True?

A、The transition state is a saddle point on the potential energy surface.;
B、One and only one of the vibrational frequencies of the transition state is imaginary.;
C、Frequency calculation is not necessary for the optimization of a reaction intermediate, which is a local minimum on the potential energy surface.;
D、After getting the transition state, one should perform an IRC calculation to confirm that it connects the desired reactant and the product.