Question

Which of the following is well-difined set?

Answer 1

Answer:

A set is well-defined if there is no ambiguity as to whether or not an object belongs to it, i.e., a set is defined so that we can always tell what is and what is not a member of the set. Example: C = {red, blue, yellow, green, purple} is well-defined since it is clear what is in the set.