CDB!

debbie

This has to do with an Easter Egg hidden inside Module 3... Please visit that post if you're curious about it!

Thanks to @RZ923 for investigating further and discovering that these types of word-puzzles are called "gramograms."

Here's a clue as to how it ended up in Module 3 in the first place:

$$ \text{ How many ways are there to arrange } 4 \text{ people in a row?} $$

$$ ABCD $$

$$ ABDC $$

$$ ACBD $$

$$ ACDB $$

$$ ADBC $$

$$ ADCB $$

$$ BACD $$

$$ BADC $$

$$ BCDA $$

$$ BCAD $$

$$ BDAC $$

$$ BDCA $$

$$ CABD $$

$$ CADB $$

$$ CBAD $$

$$ CBDA $$

$$ CDAB $$

$$ CDBA $$

$$ DABC $$

$$ DACB $$

$$ DBCA $$

$$ DBAC $$

$$ DCBA $$

$$ DCAB $$

Good luck with the gramogram puzzles!