Hmm. Let's see. I don't think it's D. And recognizing sources in stress does help, but I think the first thing is knowing that someone has too much stress, so i think the answer is A.
Answer:
True
Explanation:
Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.
It’s A! Easy! The best way to do it is by doing something about it!
