Squires arrived after the spectators, and the knights arrived (late) of all. which form of the irregular adverb late correctly completes the sentence? later last most late

Squires arrived after the spectators, and the knights arrived last of all.

The sentence means that the knights were last to come to the event, so we need the superlative form of the adverb. Later is comparative, and most late doesn't exist as a form, which leaves as with last as the only option.