Answer:
A
Explanation:
Cardiovascular diseases involves the heart. 
Any of the above options with regards to blood (etc, white blood cells, red blood cells) are related to circulatory system, not affecting the function of the heart. 
Stem cells performing apoptosis to remove old cells is a myth. Stem cells can only differentiate to form cells of the same lineage, not causing other cells to undergo apoptosis. The only external factor that can cause cells to undergo apoptosis is a type lymphocyte in the immune system
 
        
             
        
        
        
Limiting factors are resources or other factors in the environment that can lower the population growth rate. Limiting factors include a low food supply and lack of space. Limiting factors can lower birth rates, increase death rates, or lead to emigration.
        
             
        
        
        
False, because a niche is how one animal uses its habitat- many animals use many different niches