Final answer:
Adenine, guanine, and cytosine are the nitrogenous bases found in both DNA and RNA. Thymine is exclusive to DNA, whereas uracil is specific to RNA.
Step-by-step explanation:
When comparing the nitrogenous bases found in both DNA and RNA, we consider adenine (A), guanine (G), and cytosine (C) as common to both nucleic acids. Adenine and guanine are purines, which have a double-ring structure, while cytosine is a pyrimidine with a single-ring structure. Contrasting with DNA's thymine, RNA contains uracil (U) instead, which pairs with adenine just as thymine does in DNA. Therefore, the correct answer to the question, "Which of the following are found in both DNA and RNA?" includes adenine (A), guanine (G), and cytosine (C) but not thymine (T) or uracil (U) as they are exclusive to DNA and RNA respectively.