Which of the following would increase the risk of stroke?
W. Hypertension and smoking.
X. A metastatic tumour entering the circle of Willis.
Y. Atherosclerosis of the carotid arteries.
Z. Atrial fibrillation.
a. if only W, X and Y are correct
b. if only W and Y are correct
c. if only X and Z are correct
d. if only Z is correct
e. if all are correct