Which arteries join at the base of the skull to form the basilar artery?

The basilar artery is formed by the union of the two vertebral arteries at the base of the skull. These vertebral arteries ascend through the transverse foramina of the cervical vertebrae and enter the cranial cavity through the foramen magnum. Once inside the skull, they converge to create the basilar artery, which plays a critical role in supplying blood to the posterior circulation of the brain, including vital areas such as the brainstem and cerebellum.

The other options listed do not contribute to the formation of the basilar artery. The carotid arteries are responsible for supplying blood to the anterior circulation of the brain but do not join to create the basilar artery. The internal jugular veins are related to venous drainage rather than arterial supply. Lastly, coronary arteries are associated with supplying blood to the heart muscle itself and have no direct connection with the formation of the basilar artery in the cranial circulation.