If CADAVER is coded as BBCBUFQ, then which of the following words can be decoded from their respective codes?

C is replaced by B (the letter preceding it)
A is replaced by B (the letter succeeding it)
D is replaced by C (the letter preceding it)
A is replaced by B (the letter succeeding it)
V is replaced by U (the letter preceding it)
E is replaced by F (the letter succeeding it)
R is replaced by Q (the letter preceding it)

As we can see, vowels are replaced by the letter succeeding them and consonants are replaced by the letter preceding them in the alphabetical series.

To retrace a letter from a code, every letter in the code must not follow a vowel in the alphabetical series.

GYPSY will be coded as FXORX.
RHYTHM will be coded as QGXSGL.
CRYPT will be coded as BQXPS.
HYMN will be coded as GXLM.

Both RHYTHM and HYMN satisfy this condition. Therefore, option E is the right answer.