Explanation

The best clue in this sentence is its parallel structure. The judge’s “keen eye” was surpassed only by her “______ wit.”

Keen means “sharply discerning,” so you should be looking for words that denote a “sharpness,” or “bitingness,” of wit. Mordant and trenchant, both of which are close in meaning to “incisive,” are best. Don’t be confused by the other set of synonyms, assiduous and sedulous, both of which have meanings close to “diligent.”

Hence options mordant, trenchant are correct!