To form a Trade Union and get it registered under the Trade Union Act, the minimum number of workers required is 7. This means that at least 7 workers must come together and join the Trade Union. Option 1 is the correct answer.

Option 2, 25, is incorrect as it exceeds the minimum requirement.

Option 3, 100, is incorrect as it is also higher than the required minimum.

Option 4, 50, is incorrect as it is also higher than the required minimum.

It is important to note that while 7 is the minimum requirement, Trade Unions can have a larger number of workers as members.