This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Extremity, Subject name: Anatomy
Pen Test is for: 
Select and explain. 
A. Median Nerve, B. Ulnar Nerve, C. Radial Nerve, D. Posterior Interosseus Nerve
A: Median Nerve
Answer: A: Median Nerve 
Explanation: Ans. A. Median NervePen test (to check the paralysis of abductor pollicis brevis) - The patient is unable to touch the object held above the thumb at right angle to palm. This test is used to check the integrity of median nerve.