When the flashlight shines on the mirror and the wall, the surface of the mirror is very flat, and the surface will be specularly reflected, and the reflected light will be reflected back against the light of the flashlight. When people look at the side of the mirror, they will not reflect the light to the human eye, so the mirror they see is dark.
This wall is uneven. When the flashlight illuminates, diffuse reflection will occur, and the reflected light will illuminate in all directions. When people look from the side, some light will enter the human eye, so the wall they see is bright.
So choose B.