Which option shows the correct DNA base pairing?

• A. Cytosine with Adenine and Guanine with Thymine
• B. Adenine with Guanine and Cytosine with Thymine
• C. Adenine with Uracil and Guanine with Cytosine
• D. Cytosine with Guanine and Thymine with Adenine

Answer: (D)

DNA base pairing follows specific complementary rules: adenine pairs with thymine, and cytosine pairs with guanine. These pairs are held together by hydrogen bonds (A-T with two bonds, C-G with three). This pairing pattern is what keeps the two strands of the DNA ladder matched and stable. The option in question aligns with those rules by showing cytosine paired with guanine and thymine paired with adenine, which is exactly C-G and T-A pairings. The T-A pair is the same relationship as A-T, just written in the opposite order. The other options mix up the pairs or introduce uracil, which is found in RNA, not DNA, so they don’t reflect DNA base pairing.