What letters of the English alphabet have reflectional symmetry (i.e., symmetry related to mirror reflection) about.

(a) a vertical mirror

(b) a horizontal mirror

(c) both horizontal and vertical mirrors

(a) A, H, I, M, O, T, U, V, W, X, Y are the letters having a reflectional

symmetry about a vertical mirror.

(b) B, C, D, E, H, I, K, O, X are the letters having a reflectional symmetry about a horizontal mirror.

(c) H, I, O, X are the letters having a reflectional symmetry about both the vertical mirror and the horizontal mirror.