This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb, Subject name: Anatomy
Which tendon is frequently absent in the upper limb? 
Select and explain. 
A. Flexor carpi ulnaris, B. Flexor digitorum profundus, C. Extensor carpi radialis brevis, D. Palmaris longus
D: Palmaris longus
Answer: D: Palmaris longus 
Explanation: The palmaris longus may not always be present. It has a sho belly and long tendon. It originates from the medial epicondyle of the humerus. Distally, it passes over the flexor retinaculum with which its fibres mingle and is attached to the palmar aponeurosis. Reference: Clinical Anatomy for students, a problem-solving approach, Neeta v Kulkarni, 2nd edition, page no140