Answer: e. mindfulness
When alpha waves are dominant in your brain (8-12 Hz), you will feel very relaxed. This happens when you are waking up in the morning.
Alpha waves can be created thru aerobic exercise. Progressive relaxation also increases alpha waves. Biofeedback is a technique used to create alpha brain waves also, in order to prevent or treat conditions like headaches, chronic pain, and high blood pressure.
However, alpha waves are strongest when you are practicing mindfulness or meditation with your eyes closed.
Guided imagery and cognitive restructuring are not associated with brain's production of alpha waves.