A human gene called the -globin gene encodes a polypeptide that functions as a subunit of the protein known as hemoglobin. Hemoglobin is found within

A human gene called the β-globin gene encodes a polypeptide that functions as a subunit of the protein known as hemoglobin. Hemoglobin is found within red blood cells; it carries oxygen. In human populations, the β-globin gene can be found as the common allele called the HbA allele, but it can also be found as the Hbs allele. Individuals who have two copies of the HbS allele have the disease called sickle cell disease. Are the following examples a description of genetics at the molecular, cellular, organism, or population level?
A. The HbS allele encodes a polypeptide that functions slightly differently from the polypeptide encoded by the HbA allele.
B. If an individual has two copies of the HbS allele, that person's red blood cells take on a sickle shape.
C. Individuals who have two copies of the HbA allele do not have sickle cell disease, but they are not resistant to malaria. People who have one HbA allele and one HbS allele do not have sickle cell disease, and they are resistant to malaria. People who have two copies of the HbS allele have sickle cell disease, and this disease may significantly shorten their lives.
D. Individuals with sickle cell disease have anemia because their red blood cells are easily destroyed by the body.