Final answer:
The DNA molecule is shaped as a double helix with antiparallel strands, where adenine pairs with thymine, and cytosine pairs with guanine.
Step-by-step explanation:
The shape of a DNA molecule is best described as a double helix; its two strands are twisted around each other. Each strand is composed of a sugar-phosphate backbone and nitrogenous bases that pair specifically: adenine (A) with thymine (T), and cytosine (C) with guanine (G). These strands are antiparallel, which means one strand runs in the 5'· to 3· direction, while the other runs in the 3'· to 5· direction. The correct answer to the question is C. Double helix; complementary strands that are antiparallel to one another.