Answer: C
There are 9 esters: methyl butanoate, methyl 2-methylpropanoate, ethyl propanoate, propyl ethanoate, isopropyl ethanoate, and four butyl methanoates (n-butyl, isobutyl, sec-butyl, tert-butyl). Alcohols from them: isopropyl (secondary) from isopropyl ethanoate, sec-butyl (secondary) and tert-butyl (tertiary) from the two butyl methanoates. Total 3.