Ravi is married ______ a cousin of mine.

Certain adjectives and past participles in English combine with one fixed preposition when introducing the noun they relate to, and that pairing is idiomatic — fixed by convention rather than freely interchangeable with any preposition of similar general meaning. “Married” is one such word: standard English fixes a single specific preposition before the person someone is wed to, and other prepositions that express similarly related ideas (accompaniment, disposal, or general association) do not substitute for it.

In this sentence, the blank sits between “married” and “a cousin of mine”, naming the person Ravi is wed to. Because English idiom fixes exactly one preposition for this meaning, the blank must take that word, giving “Ravi is married to a cousin of mine.”

• “with” pairs with adjectives like “friends with” or “compatible with” that describe a shared relationship of similarity or association, but the fixed idiom naming who someone is wed to does not use this preposition.

• “along with” expresses doing something together with a companion (e.g., “she went along with her cousin”), describing joint action rather than the state of being wed to someone, so it does not fit here.

• “off” only combines with “married” in the separate causative idiom “marry somebody off” (a third party arranging someone else’s marriage), which needs a different sentence structure — an agent doing the marrying-off — not present in this sentence.

Therefore, the correct preposition is the one required by the fixed idiom naming who a person is wed to: “Ravi is married to a cousin of mine.”