Answer the following question: Information: - Rugby union in Spain is a growing team sport. As of 2014, there were 51,123 registered rugby union players in Spain, playing for 221 clubs in various divisions. The governing body for rugby union in Spain, the Spanish Rugby Federation (Spanish: Federacion Espanola de Rugby), founded in 1923, joined the International Rugby Board in 1988. It is also a member of FIRA. - The Copa del Rey de Rugby ( previously known as Campeonato de Espana de Rugby ) is the national rugby cup . The competition was founded in 1926 and , currently is the second most important competition after the Division de Honor de Rugby . - The Division de Honor is the top club competition for rugby union in Spain. The league began in 1953 and consists of ten teams. Clubs are relegated to and promoted from Division de Honor B. The winner each year qualifies for the European Challenge Cup, the second-tier European rugby competition. What object entity has the relation of 'sport' with the subject 'copa del rey de rugby'? Choices: - rugby - rugby union - sport
Answer:
rugby union