The correct option is A Brachialis
The brachialis is a muscle in the upper arm that flexes the elbow joint.
The Latissimus dorsi is the larger, flat, dorsolateral muscle on the trunk, posterior to the arm.
The dorsal scapular is the nerve that is the right brachial plexus with its short branches, viewed from in front.
Triceps brachii is that large muscle on the back of the upper limb and is principally responsible for extension of the elbow joint (straightening of the arm).
Therefore, the correct answer is option A.