Answer
See explanation.
Work Step by Step
Rubbing your feet on the insulating nylon rug builds up excess charge on you, which is discharged when you touch the doorknob.
On humid days, water vapor in the air makes it a better conductor, and charge can more easily leak off your body as you walk, so you don’t build up as much charge before you touch the metal object.
A small paper clip can hold less charge than a large doorknob (the excess charge that is already there, in a confined space, makes it harder for more charge to accumulate). When you touch the paper clip instead of the doorknob, you don’t transfer as much charge, reducing the shock you feel.
