The answer is either a or c
        
                    
             
        
        
        
Answer:
See the answer below
Explanation:
<em>The chance that a child from two people with sickle cell trait will have normal RBCs remains the same irrespective of the amount of oxygen in the environment.</em> From the cross:
                   AS    x    AS
             AA    AS    AS    SS
Hence, the chance of having a child with normal RBCs in both high and low-oxygen environments is  1/4  or 25%.
The chance that a child will have sickle cell disease is also 1/4   or 25%.
The possible genotypes in a Punnet's square can be seen in the attached image
 
        
             
        
        
        
Answer:
...were due to single genes and followed simple inheritance patterns (dominant/recessive).
Explanation:
The traits Mendel studied were easy to track because the two possible outcomes were distinct and the trait itself was visible and trackable.  The fact that they followed simple inheritance patterns helped him when he was determining his ratios for different crosses because complex inheritance would've muddled his data.