Pretty shore the answer is D
The most reliable source of medical health information is always a physician. Although certain websites can contribute accurate information they are not always as detailed as a physician.
I believe the correct answer for this would be C.
The passage listed above in my own words:
Ischemic strokes are the most common type of stroke. They occur when a blood vessel that leads to the brain becomes clogged usually by blood clots, which are clumps of blood that stick together. The blood sticks together in order to stop bleeding. However, they often form inappropriately inside an artery or vein , causing the blood flow to decrease and the blood can't get where it needs to be. Another reason for Ischemic strokes is because sometimes, arteries become narrow and clogged, usually with plaque, which is a mix of fatty stuff and cholesterol that stick to the walls of blood vessels.
Hope this helped! :)