Both the infraspinatus and teres minor have lines of application that produce external rotation moments around the glenohumeral joint's longitudinal axis. The subscapularis produces internal rotation of the glenohumeral joint, so 'b' is the appropriate response to this question.

The glenohumeral ligament contributes to external rotation even though the force it develops is passive. Abduction of the glenohumeral joint elongates the glenohumeral ligament and introduces tension into it. The ligament communicates this force to its humeral attachments and causes them to move in the direction of external rotation. The ligament, whose fibers' orientation is twisted when the glenohumeral joint is adducted, actually untwists itself.

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