Answer:
A) Elastin
Step-by-step explanation:
Elastin is the principle load-bearing protien present in the wall of aorta. It is the protien which coil and recoils like a spring within the elastic fibres and accounts for elasticity of blood vessels. As during excerise , afterload is increased ,thus a stretch is produced in the vessels. Similarly im warm environment the vessels dilate this this stretch is produced by elastin.