Answer:
removal of water molecule between each two units
Explanation:
The answer would be A buddy. YOU'RE WELCOME :D
You should seriously consider including the answer choices.
The only correct answer in this case is B - a stroke.
None of the other answers could be counted as correct here.
While A - a heart attack is conceptualy similar, when we're talking about a heart attack, we're talking about not enough oxygen that gets delivered to the heart - because something is blocking it.
C - hypertension on the other hand means someone has a higher blood pressure than is usual for a regular human being, which puts more strain on his cardiovascualr system.
and D - atherosclerosis doesn't come even close to be correct :)