31. For each of the following patterns, identify the rigid motions that preserve the pattern:
31.
For all parts, translations.
(a) Reflection in the horizontal midline
(b) None other than translations
(c) Reflection in the horizontal midline, reflections in vertical lines through the centers of the Hs or between them, 180° rotation around the centers of the Hs or the midpoints between them, glide reflections.
(d) Reflections in vertical lines through the centers of the Ms or between them.