Given : $I$ and $II$ are

Which of the following has both plane of symmetry and centre of symmetry

Calculate enantiomeric excees of mixture containing $6g$ of $( +) - 2$ -butanol and  $4g$ of $(-) - 2$ -butanol........$\%$

The correct statement$(s)$ about the compound $\mathrm{H}_3 \mathrm{C}(\mathrm{HO}) \mathrm{HC}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}(\mathrm{OH}) \mathrm{CH}_3(\mathbf{X})$ is(are)

$(A)$ The total number of stereoisomers possible for ${X}$ is $6$

$(B)$ The total number of diastereomers possible for ${X}$ is $3$

$(C)$ If the stereochemistry about the double bond in ${X}$ is trans, the number of enantiomers possible for ${X}$ is $4$

$(D)$ If the stereochemistry about the double bond in ${X}$ is cis, the number of enantiomers possible for ${X}$ is $2$

Configuration of given compound is

For the given compound $X$, the total number of optically active stereoisomers is. . . . . . .