I believe the answer is D: Early followers had different opinions about who would lead them. 
After the death of Prophet Muhammad, nobody knew who would lead them again, and the religion split apart into two due to this. 
According to npr, most of the Prophet Muhammad's followers wanted the community of Muslims to determine who would succeed him; a smaller group thought that someone from his family should take up his mantle. 
<em>If this is incorrect, please, don't refrain to tell me. Thank you. </em>
 
        
             
        
        
        
<span>Life-course-persistent offenders 
"may show signs of neurological impairment".</span>
Terrie Edith Moffitt suggested that there are two principle
sorts of introverted offenders in the society. The adolescence-limited offenders, who show antisocial
conduct just amid puberty and the other was life-course-persistent offenders,
who start to carry on reservedly very early in adolescence and proceed with
this conduct into adulthood. 
 
        
        
        
D. Stereotype. Hope this helps :)
        
             
        
        
        
That would be a <span>Reference Group, good luck!</span>
        
             
        
        
        
Answer:
This study was an experiment. 
Explanation:
An experiment demonstrated to compare the behavior of the two groups, the one who watched the violent film and the the one who did not. the research was made to figure out the impact of violence in human development.