There are 11 letters in the word: EXAMINATION. How many letters of this word won't be changed when the word undergoes lateral inversion in a plane mirror?

The correct option is C 8
The letters which have vertical axis of symmetry will remain unchanged under lateral inversion. Therefore, the letters X, A, M, I, T and O are the 8 letters(A and I repeating twice) in total that won't be changed after reflection from a plane mirror.