Final answer:
The backbone of the DNA molecule is made up of alternating E) phosphates and B) pentoses (deoxyribose), linked by phosphodiester bonds, with nitrogenous bases attached.
Step-by-step explanation:
The "backbone" of the DNA molecule is composed of alternating phosphates and pentoses, which serve as the structural framework to which the nitrogenous bases are attached. The phosphates and pentoses (a 5-carbon sugar called deoxyribose in DNA) form a repeating pattern along the length of the DNA strand, creating a sturdy scaffold for the genetic material. These components are linked together by phosphodiester bonds, which are covalent bonds between the phosphate group of one nucleotide and the pentose sugar of the next. The nitrogenous bases, which include adenine, cytosine, guanine, and thymine, protrude from the backbone and through complementary base pairing, with adenine pairing specifically with thymine and cytosine pairing with guanine, form the rungs of the DNA "ladder" and ultimately the encoded genetic information. This structure is stabilized further by hydrogen bonds between the complementary bases.