B is not possible. RNA contains only adenine, cytosine, guanine and Uracil instead of Thymine. The rest are correct because Adenine pairs with either uracil (RNA) or thymine (DNA) and cytosine pairs with Guanine
The correct answer is B, as a DNA adenine cannot bond with an RNA thymine since RNA contains uracil instead of thymine. The other options represent valid pairings based on base pairing rules. This reflects the fundamental differences between DNA and RNA structures.
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