Answer: B — TSPO

In the given code, ZERO is encoded as ADSN.

Observe the pattern:

• Z is changed to A.
• E is changed to D.
• R is changed to S.
• O is changed to N.

So, the pattern is:

• 1st letter: next letter
• 2nd letter: previous letter
• 3rd letter: next letter
• 4th letter: previous letter

Applying the same pattern to STOP:

• S becomes T.
• T becomes S.
• O becomes P.
• P becomes O.

Therefore, STOP is encoded as TSPO.