Final answer:
A reducing coupling with ID threads on both ends is used to connect pipes of different diameters.
Explanation:
The pipe fitting that has ID threads on both ends and joins two pipes of different diameters is a reducing coupling. This type of fitting allows for a connection between pipes with varying diameters by providing a smooth transition from a larger pipe to a smaller one.
Learn more about pipe fittings and connections here:
https://brainly.com/question/36720918
