A health professional is trying to find an exact location on a patient's shoulder to inject pain-relieving medication into the shoulder joint. Which of the following bone markings would the doctor most likely feel for to locate the exact area needing the injection?

a. the epicondyle on the humerus
b. the trochanter on the clavicle
c. the tubercle on the humerus
d. the tuberosity on the scapula