Ans: A
I must be true. The 9 planes of reflection are shown below.
I must be true. The 9 planes of reflection are shown below.
II must be true. The intersection point of all axes of rotational symmetry is shown below.
III may be false. According to the figure above, the angle between $a$ and $d$ is not $90^\circ$. It is $45^\circ$.
