In Optimality Theory (OT), the candidate that best satisfies the constraints is chosen as optimal. In this problem, we are provided with the constraint ranking of COMPLEX, DEP-IO >> MAX-IO, where:
- COMPLEX penalizes complex structures (e.g., multi-syllabic forms).
- DEP-IO penalizes input-output faithfulness, specifically disallowing the insertion of segments in the output.
- MAX-IO penalizes the deletion of input segments in the output.
For the input /spun/, the candidate [pun] is optimal because:
- It satisfies the constraint COMPLEX by avoiding unnecessary complexity (the input structure /spun/ is reduced to a simpler form).
- It does not violate the DEP-IO constraint because no input segments are inserted.
- It minimally violates MAX-IO because no segments are deleted.
Option (A) [su.pun] introduces a complex structure, violating COMPLEX.
Option (C) [sun] involves a deletion (the segment 'p' is deleted), violating MAX-IO.
Option (D) [is.pun] introduces an unnecessary segment, violating DEP-IO.
\[
\boxed{\text{The correct answer is (B).}}
\]