No it is not the main energy source
        
             
        
        
        
Answer:
Blood leaves the heart through the pulmonic valve, into the pulmonary artery, and to the lungs.
Explanation:
Hope this helps.
 
        
                    
             
        
        
        
Answer:
"Knowing your Basal Metabolic Rate is important whether you want to maintain your weight, lose weight, or even gain weight. Your BMR can help determine what number of calories you should be eating in order to meet your goals. If you want to lose weight, you will need to eat less than your BMR (or maintenance calories)"
"The higher your BMI, the higher your risk for certain diseases such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers"
so basically its the energy that requires your body to work while you sit idle.  but the reason above is the importance of caculating the BMR. This is what I researched, but feel free to look more in depth about it if I didnt clear it up :)
Explanation:
"Your Basal Metabolic Rate (BMR) is the minimum level of energy your body needs when at rest to function effectively including your respiratory and circulatory organs, neural system, liver, kidneys, and other organs (you even burn calories when sleeping).  About 70% of calories consumed every day are used for your basal metabolism."
 
        
             
        
        
        
Answer:
It's normal for a baby to show his first tooth as early as four months, or a late child could be 15 months . A few babies are even born with a tooth! A child should be between two and a half years old or three years old before he/she has a full set of their teeth .
 
        
                    
             
        
        
        
<u><em>Digestive</em></u> is a system prepares food for absorption into the bloodstream.So the answer for your question is Digestive.
Hope this helps:)