IUPAC name of the given compound is

• The compound contains 3 methyl groups and one ethyl group attached to the parent hydrocarbon of 6 carbon atoms. It is a carboxylic acid.
• The compound contains a carboxylic acid group. The numbering is done from that carbon atom which has $-\mathrm{COOH}$ attached to it as it has higher priority than the $-\mathrm{OH}$ group.
• Hence, there is $-\mathrm{COOH}$ present at position 1, $-\mathrm{OH}$ group is present at position 5, three methyl groups present at positions 2,3,4 respectively. A double bond is present at the position 3 in the carbon chain.

so the correct IUPAC name is 5-Hydroxy-2,3,4-trimethyl-3-hexenoicacid