The dots and dashes in each square,
when decoded as Morse code, spell out "THIS IS A POLYBIUS SQUAR".
From this, we can assume that the correct choice is
answer B, since it properly finishes the message as "THIS IS A POLYBIUS SQUARE".
With a bit of help from the hint,
which mentions the word “regular”, I then looked at all of the squares with regular polygons in the grid. The corresponding letters from the Polybius square, in order of the number of sides in the regular polygon, gives the phrase “OF THE”, which doesn’t seem like an answer. Reading the morse from the answer choices normally gives “NEON”, but reordering the regular polygons by side number and extracting the morse again gives “NONE”, which seems relevant. Both phrases seem close to spelling out “NONE OF THEM”, which may answer the question “Which of these is the answer?”, but M’s shape is a non-regular rectangle, so it seems dubious.
I’ll keep this data here for convenience’s sake.
Polybius square ("I" is actually "I/J"):
Number of sides ("A" represents 10 for spacing reasons):
Letters sorted by shape:
0 = CGPY
1 = DRX
2 = ANQU
3 = ILOSW
4 = FKMV
5 = T
6 = HZ
7 = E
Polybius viable numbers: