Final answer:
The most likely cause of the headaches described is tension. Tension headaches occur due to muscle tension in the shoulders, neck, and head, often caused by stress.
Step-by-step explanation:
The most likely cause of the headaches described in the question is tension. Tension headaches occur when the muscles in the shoulders, neck, and head become too tense, often as a result of stress. These headaches are the most commonly experienced type of headache and can be relieved by relaxation techniques and mild pain relievers such as ibuprofen.