Answer:
stethoscope is the instrument used to measure heart beat
 
        
                    
             
        
        
        
When you shiver, that's actually how you help yourself stay warm! It's your immediate instinct reaction to do so when you're cold, so there will be more heat produced, and they occur by your muscles moving. =)
        
             
        
        
        
Proteins are made up of 20 different amino acids