A knife wound to the neck damages the posterior cord of the brachial plexus. Which of the following muscles would be most likely to be paralyzed?

The posterior cord supplies the axillary and radial nerves. Of the muscles listed, only the deltoid is supplied by one of these two nerves, specifically the axillary nerve. The flexor carpi ulnaris is supplied by the ulnar nerve.The flexor digitorum superficialis, the flexor pollicis brevis, and the palmaris longus are supplied by the median nerve. Ref: Moon D.A., Foreman K.B., Albeine K.H. (2011). Chapter 30. Shoulder and Axilla. In D.A. Moon, K.B. Foreman, K.H. Albeine (Eds), The Big Picture: Gross Anatomy.