Final answer:
The IUPAC name for the ester from butanoic acid and ethanol is ethyl butanoate, which is option D in the multiple-choice question.
Step-by-step explanation:
The IUPAC name for the ester formed from butanoic acid and ethanol is ethyl butanoate. The naming of an ester involves taking the alkyl group from the alcohol and the acyl group from the acid. For the alcohol ethanol, the alkyl group is ethyl. For the acid butanoic acid, replace the word acid with 'oate' to get butanoate. Therefore, the correct IUPAC name is ethyl butanoate, which corresponds to option D.