The answer is D.
The longer life expectancy
Hope this helps :)
        
                    
             
        
        
        
Meiosis produces cells (germ cells or gametes) with only half the DNA, or chromosomes, as normal cells (somatic cells). This is called haploid or referred to as "n" number of chromosomes. Normal body cells have doubke that, called "2n," or diploid. For humans our n = 23, so germ cells (haploid) have only 23 chromosomes, while somatic (normal body) cells have "2n" or 46 chromosomes. It is important to only carry half the number of chromosomes or DNA (n), because it is going to combine with another half (n) when sperm meets egg during fertilization. This n + n = 2n restores the diploid number of chromosomes (DNA) in a zygote, the first cell of a future embryo, fetus, and new human being.
        
             
        
        
        
Robert Hooke observed the cells through a combination of lenses. 
After Robert Hooke, the development of microscopy take place. After the development of the microscopy, scientist were able to observe the features of the cell. In order to formulate a cell theory observation of most of the cells was necessary. So, it was necessary to observe different types of cells from different organism. So, the advancement of the microscopy and observation process required for the formulation of the cell theory was the reason for the delayed development of the cell theory.
 
        
             
        
        
        
Answer:
B. Virus
Explanation:
Once attached to a host cell, a virus injects its nucleic acid into the cell. The nucleic acid takes over the normal operation of the host cell and the host cell produces multiple copies of the virus.