A) The phosphodiester backbones would be too close and repel one another.
B) There would be no discernable difference between DNA strands aligned in a parallel versus an antiparallel manner.
C) Complementary nucleotides would line up normally; but fewer hydrogen bonds would form, so the strands could be more easily pulled apart.
D) Some regions of the two strands may form atypical hydrogen bonds, but the overall structure of the two DNA strands would not be stable.
E) Complementary nucleotides would be attracted to each other, forming ionic bonds that would make the helix stable but not uniform in width.