Question: which third annual Arrowverse crossover event did "Medusa"  features 
Sentence (from "Flash vs. Arrow"): The crossover sees Team Flash (Barry Allen / Flash, Caitlin Snow, and Cisco Ramon) helping Team Arrow (Oliver Queen / Arrow, Felicity Smoak, and John Diggle) take on the boomerang-wielding villain Captain Boomerang, while Team Arrow helps Team Flash confront the metahuman Roy Bivolo.
Relevant evidence: No