Answer:
See the answer below
Explanation:
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. 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 Â or 25%.
The possible genotypes in a Punnet's square can be seen in the attached image