Veins<span> have low </span>blood<span> pressure compared to </span>arteries<span> and need the </span>help<span> of </span>skeletal muscles<span> to bring </span>blood back to the heart<span>. Most </span>veins<span> have one-way valves called venous valves to </span>prevent<span> backflow caused </span>by<span> gravity. They also have a thick collagen outer layer, which helps maintain </span>blood<span> pressure and </span>stop blood<span> pooling. So your answer would most likely be A</span><span />
