The Genes for the Normal Mutant Alleles of a Gene

The genes for the normal mutant alleles of a gene are cut with the same restriction enzyme. The resulting DNA fragments were separated by gel electrophoresis, producing the gel shown in the figure below. Why are the patterns produced by these two alleles different?

A) The normal hemoglobin gene is cut by two restriction enzymes, but the sickle cell anemia allele is cut by only one restriction enzyme.
B) The gene for the normal allele is much larger than the gene for sickle cell anemia.
C) The gene for the normal allele has a sequence recognized by DdeI, but the gene for sickle cell anemia does not.
D) The sickle cell allele has the ability to produce ligase to repair the damage done by restriction enzymes, but the normal allele does not.