Which of the following compounds is optically active?

The concentration of an organic compound in chloroform is $6.15 \ g$ per $100 \ mL$ of solution. $A$ portion of this solution in a $5 \ cm$ polarimeter tube causes an observed rotation of $-1.2^{\circ}$. What is the specific rotation of the compound?

Among the following,which one can have a meso form?

The two enantiomers of secondary butyl chloride differ from each other in which one of the following properties?

The separation of a racemic mixture into pure enantiomers is termed as

$d$-tartaric acid and $meso$-tartaric acid are