Final answer:
The claim about nucleosides and nucleotides is false. Both DNA and RNA consist of nucleotides, which include different sugars and bases. DNA includes thymine while RNA contains uracil instead.
Step-by-step explanation:
The statement that nucleosides are found only in RNA while nucleotides are found only in DNA is false. Both DNA and RNA are polymers of nucleotides. Each nucleotide consists of a base, a pentose sugar (either ribose in RNA or deoxyribose in DNA), and phosphate groups. The bases in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T), while in RNA, thymine (T) is replaced by uracil (U), but the other three bases are present in both DNA and RNA.
It's also false that A, C, G, and T represent the bases in RNA. In RNA, the letter U (uracil) replaces the T (thymine) found in DNA. Moreover, RNA typically forms a single-stranded structure, not a double helix like DNA.