D.
A fixed allele is homozygous within a population so D should be the correct answer.
Hope this helps!
        
             
        
        
        
Answer: If a mutation occurred in Silencer of Death Domain (SODD) that prohibited its interaction with the DD of TNF receptor, the TNF receptor would evoke its response by binding to a transmembrane receptor, TNFR1. 
Explanation: Binding to TNFR1 inhibits the recruitment of cytoplasmic signaling proteins to TNFR1 to prevent recruitment of a number of protein (TRADD) or prevent spontaneous aggregation of the cytoplasmic death domains of TNFR1 molecules.
SODD mechanism is useful in preventing unwarranted TNFR1 activation in the process of apoptosis. 
 
        
             
        
        
        
Answer:
legth of life is the answer 
 
        
             
        
        
        
Test tube babies are a babies conceived by in vitro fertilization.
in virto fertilization is a process by which an egg is fertilised by sperm outside the body.
hope this helps :)
        
             
        
        
        
Answer:
to illustrate key points simply.
Explanation:
You first use images to back up your evidence, then secondly use them to add aesthetic value to your slide