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
Flexion of metacarpophalangeal joint and extension of interphalangeal joints is major action of 
Select and explain. 
A. Palmar interossei, B. Dorsal interossei, C. Lumbricals, D. FDS
C: Lumbricals
Answer: C: Lumbricals 
Explanation: It is the action of lumbricals.The dorsal interossei abduct the fingers. the palmar interossei adduct the fingers.The FDS flexes middle phalanx at PIP joints. ref :textbook of anatomy upper limb and thorax ,vishram singh ,2nd edition ,page no.144