Which of the following compounds is an optically active substance with a low molecular weight?

Which of the following acids does not exhibit optical isomerism?

Two possible stereo-structures of $CH_3CH(OH)COOH$,which are optically active,are called

Separating of $d$ and $l$ enantiomorphs from a racemic mixture is called

The correct statement$(s)$ about the compound $H_3C-CH(OH)-CH=CH-CH(OH)-CH_3$ $(X)$ 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 $2$.

Which one of the following shows optical activity?