Question $8$

Suppose $s=\{1,2,4,3\},$ what happens when invoking s$.$add$(4)?$

There is no add method for a set object.

This method is executed fine and $4$ is not added to the set since $4$ is already in the set.

This method is executed fine and $4$ is added to the set.

Since $4$ is already in the set, Python raises a KeyError exception.