The answer is D. Thymine, as it is one of the nitrogenous bases that form the rungs of a DNA strand. The rungs consist of paired bases: adenine pairs with thymine and guanine pairs with cytosine. The other options do not belong to the rungs structure of DNA.
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The correct answer is thymine, as it is one of the nitrogenous bases found in the rungs of a DNA strand. The rungs of DNA consist of two paired bases, adenine with thymine, and guanine with cytosine. Other options listed do not belong to the rungs of DNA. ;