Which nitrogen bases are present in DNA?

The correct answer identifies the specific nitrogen bases that are found in DNA. DNA contains four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These bases pair in a specific way: adenine pairs with thymine and guanine pairs with cytosine, forming the rungs of the DNA double helix structure.

The presence of uracil (U) in some options can lead to confusion. Uracil is found in RNA, where it replaces thymine. Therefore, any choice including uracil is incorrect for DNA. In addition, while adenine (A), thymine (T), cytosine (C), and guanine (G) are the correct bases for DNA, choices that do not include thymine or incorrectly claim the presence of uracil reflect a misunderstanding of nucleic acid composition. Hence, focusing on the specific combination of adenine, guanine, cytosine, and thymine is essential for accurately identifying the bases in DNA.