IUPAC name of the compound is 3-Methylpent-2-ene-1,2-diol.

The number of longest carbon atoms chain in the above structure is 5. All the bonds between the carbon atoms are single bonds except one, a double bond between C₂ and C₃ atoms. So, the IUPAC name of the longest carbon chain is pent-2-ene. Two –OH groups are attached to the Carbon atoms at position 1 and 2 and one methyl group at 3^rd position. Therefore, the IUPAC name of the above compound is 3-Methylpent-2-ene-1,2-diol.