You can draw lines from the center of the hexagon to the peak. And you can find that this hexagon is divided to 6 parts. Every 60° can the hexagon map onto itself. So at 60,120,180,240,300 and 360 total 6 times.
A penny is not that large, and you can fit multiple pennies in the palm of your hand. This means that the only reasonable measurement is 19 mm, (& 8 cm, but that is only if you have really large hands). Therefore, (A) is your choice.
