Final answer:
The most common site of arterial occlusion by an embolus is the middle cerebral artery in the brain.
Step-by-step explanation:
The most common site of arterial occlusion by an embolus is the middle cerebral artery, which supplies blood to the temporal and parietal lobes of the brain. When a clot breaks off from a plaque or forms in the heart because of arrhythmia, it can travel to the brain and become lodged in an artery, blocking blood flow. This can lead to an ischemic stroke, which occurs when the blockage prevents oxygen from reaching brain cells and causes their death.