Give a stream of consciousness and then the final answer. A lower pair is an ideal joint that constrains contact between a surface in the moving body to a corresponding surface in the fixed body. A lower pair is one in which there occurs a surface or area contact between two members, e.g. nut and screw, universal joint used to connect two propeller shafts. Cases of lower joints:

Answer this question: universal joint is an example of which pair?
The relevant information is: A lower pair is one in which there occurs a surface or area contact between two members, e.g. nut and screw, universal joint used to connect two propeller shafts.
So, the final answer is A lower pair.