CHXII12:ALDEHYDES KETONES AND CARBOXYLIC ACIDS
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The correct nomenclature for the following compound is
1 2-Carboxy-4-hydroxyhept-6-enal
2 2-Formyl-4-hydroxyhept-6-enoic acid
3 2-Formyl-4-hydroxyhept-7-enoic acid
4 2-Carboxy-4-hydroxyhept-7-enal
Explanation:

So, the correct answer is (4).