Intetesting question. Its important to know what our goal is because that is the only way to know if we are on track. If we want to loose weight we have to have goal of how much. When we make small success than we will be encouraged to do more and it will impact our health and positive attitude.
All of these but the nosebleeds seem correct, but something much stronger like cocaine can cause nosebleeds.
But if you want just ONE answer 'impaired memory and learning' seems like the best one to pick because that is one of the most noticeable signs of marijuana use.
This website talks about the symptoms of use, I trust its accuracy:
https://www.webmd.com/mental-health/addiction/marijuana-use-and-its-effects#1
I believe it’s carbon dioxide, because you use your respiratory system to breathe in oxygen, and oxygen goes through your circulatory system. And you breathe out CO2.
