Which of the following is an example of two sets?
-changing activities twice in a workout to "confuse" the muscles
-two different muscles responding to an action at one time
-five sit-ups followed by a rest and then five more sit-ups
-a workout journal that details monday's and tuesday's activities

the answer would be 5 sit-ups, rest, then 5 more because you should always rest in between work outs to prevent straining your self.

Five sit-ups followed by a rest and then five more sit-ups is an example of two sets.

Sets is the number of times that an exercise is repeated for the set number of repetitions. For example if an individual perform 10 squats and rest followed by another 10 squats and rest and then another 10 squats. The person has completed three sets of 10 repetitions. From the question given, five sit-ups followed by a rest and then five more sit-ups is an example of two sets.