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 of the following is a modification of deep fascia? 
Select and explain. 
A. Extensor retinaculum, B. Palmar aponeurosis, C. Fibrous flexor sheath, D. Plantar aponeurosis
A: Extensor retinaculum
Answer: A: Extensor retinaculum 
Explanation: The extensor retinaculum is a thickened deep fascia on the posterior aspect of hand that protects the extensor tendons and prevents their bowstringing.The palmar aponeurosis is the degenerated tendon of palmaris longus.The flexor tendons lie in the fibrous flexor sheaths.Reference: Textbook of anatomy, Upper limb, and thorax, Vishram Singh, 2nd edition, page no.142,143,123