Among the following, the Newmann projections of meso- $2, 3$ -butanediol are
$P, Q$
$P, R$
$R, S$
$Q, S$
The following compounds differ in respect of
Which one of the following pairs represents stereoisomerism
Disymmetric object is one which is
The optically inactive compound from the following is
The number of stereoisomers possible for a compound of the molecular formula
$CH_3 -CH = CH -CH( OH)-Me$ is :