Which muscle is primarily responsible for the initiation of abduction of the arm in the frontal plane____________________?

A. Infraspinatus
B. Supraspinatus
C. Teres major
D. Subscapularis

The supraspinatus muscle is located on the upper part of the scapula and plays a crucial role in initiating abduction of the arm in the frontal plane. It helps to lift the arm for the first 15 degrees, after which other muscles like the deltoid take over.

The correct answer to the question: "Which muscle is primarily responsible for the initiation of abduction of the arm in the frontal plane____________________?" is "Supraspinatus".