The process of separation of pure from racemic mixture is known as resolution of racemic mixture.

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

The Fischer projection of $\mathrm{D}$-erythrose is shown below.

$\mathrm{D}$-Erythrose and its isomers are listed as $\mathrm{P},\mathrm{Q},\mathrm{R},$ and $\mathrm{S}$ in Column I. Choose the correct relationship of $\mathrm{P},\mathrm{Q},\mathrm{R},$ and $\mathrm{S}$ with $\mathrm{D}$-erythrose from Column II.

	Column - I		Column -II
P.		1.	Diastereomer
Q.		2.	Identical
R.		3.	Enantiomer
S.

Which of the following carbonyl compounds will exhibit enolization?

(i) 

(ii)

(iii) 

(iv) 

(v) 

The absolute configurations of the following compounds  respectively, are

The correct statement about the following compounds

is