Using a pedometer during mile run.
You're doing a mile run, which helps with cardiovascular endurance. That isn't muscular endurance, so cross that off.
Using a ruler to measure sit and reach results.
If you feel the tension or pain in your legs and back, that's flexibility, so this is not the right one either.
Using a scale to measure body weight.
I do not think this is even a type of exercise. You're just measuring your BMI and weight when you do this kind of thing.
I'd say it's "Using stop watch to count number of pull-ups."
I think it is this one because, everyone's body is different.