Do you want the catholic answer or do you just want a general answer, because it could be an opinion.
        
                    
             
        
        
        
I believe that hair and limbs are homology because all mammals have hair and similar limb structure. Hair loss and social behavior on the other hand are homolasy because not all mammals have them. Homology is the similar traits due to common ancestry while homoplasy is similar traits for other reasons other than common ancestry. 
        
             
        
        
        
<span>The exosphere is the fifth and final layer of the atmosphere. This layer is a little thicker than the theremosphere at 500-1000 km thick.</span>
        
             
        
        
        
D. Cross braces this is the right answer
        
             
        
        
        
As a rule of thumb, in order to improve the reliability and accuracy of an experiment, it is best if the experiment is repeated several times. The increased number of trials ensures that the readings observed have minimal random error.