The question asks us to identify the incorrectly drawn DNA base structure among four given structures.

However, in the provided prompt, the actual structures for options A, B, C, and D are missing. Since the question depends entirely on inspecting those structural formulas, it is not possible to independently determine which option is incorrect without seeing them.

Step 1: What bases are present in DNA?

DNA contains four nitrogenous bases:

1. Adenine — a purine
2. Guanine — a purine
3. Cytosine — a pyrimidine
4. Thymine — a pyrimidine

Step 2: Correct standard structures to compare against

To identify an incorrect structure, we would compare each option with the known base formulas:

• Adenine: $6$-aminopurine
• Guanine: $2$-amino-$6$-oxopurine
• Cytosine: $4$-amino-$2$-oxopyrimidine
• Thymine: $5$-methyl-$2,4$-dioxopyrimidine

A common trap is drawing uracil instead of thymine.

• Uracil lacks the methyl group at the $5$-position.
• Thymine has a $-CH_3$ group at the $5$-position.

Step 3: Why the answer cannot be fully derived from the prompt

Because the option structures are not shown, I cannot verify whether option D is indeed the incorrect one.

Step 4: Comparison with stored answer

The stored correct answer is D, but since the structural diagrams are absent, I cannot independently confirm it from the given information.

If the missing option D corresponds to an incorrectly drawn DNA base (for example, uracil in place of thymine, or wrong placement of amino/oxo groups), then D would be correct.

So, based only on the stored key and common exam patterns, D is plausible, but not rigorously derivable from the prompt as written.