Examine the Figures Above and Answer the Following Question(s)

Examine the figures above and answer the following question(s) . In the figure above, the two strands have separated in step "b" because

A) the sugar-phosphate bonds were broken.
B) the hydrogen bonds between bases were broken.
C) energy from primers pushed the bases apart.
D) the bases, being negatively charged, repelled each other.
E) proteins were inserted between each pair of bases.