Acetone on addition to methyl magnesium bromide forms a complex, which on decomposition with acid gives $\underline {X}$ and $Mg(OH)Br$. Which one of the following is $\underline X$?

Question

$$\begin {array} {1 1} (1)\;CH_3 OH & \quad (2)\;(CH_3)_3COH \\ (3)\;(CH_3)_2CHOH & \quad (4)\;CH_3 CH_2 OH \end {array}$$