Step 1: Understand the literal meaning of the word “harness.” A harness is the working equipment placed on a horse when it is actively engaged in pulling or labor. Figuratively, being “in harness” suggests being actively involved in work or duty.
Step 2: Interpreting the expression idiomatically, the phrase refers to a situation in which a person dies while still engaged in his job or active service, rather than after retirement or withdrawal from work.
Step 3: Among the given options, option (C) accurately conveys the idea of dying while still actively working. Hence, it is the correct answer.