Concept:The word "then" contains the voiced "th" sound /ð/.We need the option with the same consonant sound.Explanation:The underlined letters "th" in "then" are pronounced as the voiced sound /ð/.Check each option:• "wealthy" has "th" pronounced as /θ/ (unvoiced).• "smooth" has "th" pronounced as /ð/ (voiced).• "den" uses "d" /d/, not "th".• "thaw" has "th" pronounced as /θ/ (unvoiced).Only "smooth" shares the voiced /ð/ sound with "then".Answer:B. smooth