Pros of using email messages is no one knows your number. By knowing your number then they have access to your area code and can eventually find out where you are located. A con of using email messages you cannot call someone and hear their voice.
The circulation that disperses oxygen & rich blood throughout the body, is "Systematic Circulation."
I believe the answer is a.
Answer:
Oxygen
Explanation:
Your cells use oxygen for energy, as a result makes carbon dioxide