What Aspect of the DNA Structure Allows to Have So

Multiple Choice

What aspect of the DNA structure allows to have so much genetic variability?

A) All organisms follow Chargaff's rules of A =T and G =C.
B) The bases connected to the sugar-phosphate backbone can be in any order.
C) The nucleotides are joined and produces a sugar-phosphate backbone.
D) There are 4 different nucleotide building blocks.
E) There is complementary base pairing between the two strands.