The correct answer is option 4: Concurrent. The Seventh Schedule of the Constitution of India divides the legislative powers between the Union (central) government and the State governments. It consists of three lists - Union List, State List, and Concurrent List. The Union List contains subjects on which only the Union government can make laws, the State List contains subjects on which only the State governments can make laws, and the Concurrent List contains subjects on which both the Union and State governments can make laws. Trade Unions are included in the Concurrent List, which means that both the Union and State governments have the power to make laws regarding trade unions. This allows for coordination and cooperation between the central and state governments in legislation pertaining to trade unions.