# Which of these is the answer?

This puzzle is part of the Monthly Topic Challenge #2: IQ Puzzle Parody

I've been playing around with my favorite IQ puzzle app, and I got to this 5x5 that's completely stumped me. Can you figure out whether the answer is A, B, C, or D?

Hint:

It's strange, I can usually solve these on a regular basis.

Hint 2:

There's one tag that hasn't been used yet and there's one square that hasn't been used yet.

• @ACB probably not with 100% confidence, but if you take the fragments found in SeptaCube's answer and apply the remaining tag to it (much like M Oehm did in the comments below it) you'll find a much more concrete solution Dec 31, 2022 at 3:58

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.

Message:
THIS
IS A
POLYB
IUS S
QUARE
Polybius square ("I" is actually "I/J"):
ABCDE
FGHIK
LMNOP
QRSTU
VWXYZ
Number of sides ("A" represents 10 for spacing reasons):
2A017
40634
34230
21352
43106
Letters sorted by shape:
0 = CGPY
1 = DRX
2 = ANQU
3 = ILOSW
4 = FKMV
5 = T
6 = HZ
7 = E
10= B
Polybius viable numbers:
21434342321352431

• you've got the first step, but there is in fact more to the puzzle than this. keep at it! Aug 4, 2022 at 21:04
• This explains the dot/rectangle sequence, but not the shapes. I think there's more to it than just the number of sides, because every (non-blank) shape is different (if rotations are relevant). Except for the ? square, which duplicates an already-seen shape. Aug 5, 2022 at 23:28
• almost there now! I'll give you two more hints. one is a tag that you haven't used, and the other is a square that you haven't used Aug 6, 2022 at 16:47
• Well done! I think rot13(gur svir-gvzrf-svir fdhner naq gur bcgvbaf ner frcnengr cnegf bs n erohf, naq gbtrgure jvgu gur fdhner jvgu gur dhrfgvba znex, juvpu unf na R va gur svefg zrffntr, lbh trg: "R. Abar bs gur nobir") Aug 7, 2022 at 8:42
• yeah, @MOehm's basically got it. the one thing is that rot13(gur R sebz gur dhrfgvba znex vf fhccbfrq gb or cneg bs gur svefg zrffntr, abg gur nafjre) Aug 7, 2022 at 22:30