Which one of the following acids does not exhibit optical isomerism?

Which one among the following cannot exhibit enantiomerism ?

The separation of racemic mixture into pure enantiomers is termed as

Which of the following compound is non-resovable (meso) compounds ?

Lactic acid in which a methyl group, a hydroxyl group, a carboxylic acid group and a hydrogen atom are attached to a central carbon atom, shown optical isomerism due to the molecular geometry at the

The number of all the possible stereoisomers formed by the given compound is