A secondary alcohol has the OH group on a carbon bonded to exactly two other carbon atoms. Analyzing each structure:
I contains only primary alcohols and carboxylic acid.
II has OH on a carbon bonded to two other carbons (secondary alcohol).
III has tertiary and primary alcohols only.
IV has secondary alcohols on the cyclopentanone ring.
V has OH on a secondary carbon (between two CH groups).
VI has the central carbon as tertiary with three OH groups.
Compounds II, IV, and V contain at least one secondary alcohol, giving total = 3.
