Normal red blood cells slide easily through narrow blood vessels. In sickle cell disease, many red blood cells change to a crescent shape like a slender moon. Crescent-shaped blood cells cause blockages in blood vessels. These blockages decrease the transport of oxygen. People with sickle cell disease often have sharp pains due to the lack of oxygen in parts of the body.

The sickle cell version of the gene that causes sickle cell disease is recessive. Suppose that two parents with no symptoms have a child with sickle cell disease. What genes did the child inherit from the parents?
A. The child must have inherited the sickle cell gene from the mother and the normal gene from the father.
B. The child must have inherited the normal gene from the mother and the sickle cell gene from the father.
C. The child must have inherited sickle cell genes from both parents.
D. The child must have inherited normal genes from both parents.