You are presented with the question "What relaxes, thereby causing aneurysms?" and the following answer choices: 
- layers of fat
 - Veins and arteries.
 - sweating
 - matter vibrating
 - blood vessels
 - the skin
 - Chemical energy
 - sensory neurons

Now knowing that dilation occurs when cell walls relax and an aneurysm is a dilation of a blood vessel, choose the best answer.


 

     blood vessels    