Union shop, closed shop, preferential shop are known as: 

• Union Shop, Closed Shop, and Preferential Shop are arrangements that require workers to join or maintain membership in a trade union as a condition of employment. • These arrangements are designed to strengthen the bargaining power and stability of trade unions. They are therefore collectively known as Union Security Measures. Why not the other options? • B. Industrial Actions → refers to strikes, lockouts, picketing, etc. • C. Organizational Security Measures → not a standard term used in industrial relations to describe these practices. • D. All the above → not correct since only Option A fits.