Which of the following is true regarding DNA structure?
A. Hydrophobic portions of DNA are found outside the helix, and hydrophilic regions are buried inside the helix.
B. Adding high heat to complementary strands of single-stranded DNA leads to strand annealing.
C. DNA is found in varied shapes consisting of single, double, and triple stranded sections.
D. A 3' hydroxyl group on the deoxyribose is required for DNA chain extension.