This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Anatomy
Extension at MCP joint is by 
Select and explain. 
A. Extensor Digitorum, B. Dorsal Interossei, C. Palmar Interossei, D. Lumbricals
A: Extensor Digitorum
Answer: A: Extensor Digitorum 
Explanation: (A) Extensor Digitorum # Extensor digitorum muscle actions include Extension of interphalangeal, metacarpophalangeal and wrist joints.> All Palmar interossei adduct the digit to which they are attached towards the middle finger + flex the digit at MCP joint & extend IP joints.> All Dorsal interossei abduct the digits away from the line of the middle finger + flex the digit at MCP joint & extend IP joints.> Lumbrical muscles flex the metacarpophalangeal joints, and extend the interphalangeal joints of the digit into which they are inserted.