Which of the following statements is FALSE?

Which of the following statements is FALSE?
 
  a. Sickle-cell anemia can result in impaired blood circulation.
  b. Individuals with sickle-cell anemia inherited an abnormal allele from each parent that causes the production of an altered form of hemoglobin.
  c. People with sickle-cell trait are as severely affected as those with sickle-cell anemia.
  d. The abnormal form of hemoglobin in people with sickle-cell anemia is called hemoglobin S.
  e. The mutation that results in sickle-cell anemia affects the hemoglobin beta chain.