How is gel electrophoresis used to demonstrate the molecular basis of SCD?

How is gel electrophoresis used to demonstrate the molecular basis of SCD?
 
  A) by revealing that the protein products of the A and S alleles have distinctive electrophoretic band patterns
  B) by revealing variations in the length of a DNA restriction fragment that distinguishes the A and S alleles
  C) by revealing variations in the exon splicing of the mRNA products of the A and S alleles
  D) by revealing variations in the electrophoretic mobility of proteins and the restriction fragment length polymorphisms of DNA (both A and B)
  E) by revealing variations in the electrophoretic mobility of proteins, the restriction fragment length polymorphisms of DNA, and the splice variants of the mRNA (A, B, and C)