Which of the following capital letters is chiral?

Which of the following is optically active?

Stereoisomers which are not the mirror images of one another are called

Find the enantiomers of the structures in Column-$(I)$ from Column-$(II)$.

Column-$(I)$	Column-$(II)$
$(A)$ $C_2H_5-C(CH_3)(OH)-H$	$(p)$ $Cl-C(Br)(I)-H$
$(B)$ $Br-C(Cl)(I)-H$	$(q)$ $OH-C(CH_3)(C_2H_5)-H$
	$(r)$ $H_5C_2-C(OH)(CH_3)-H$
	$(s)$ $Cl-C(I)(Br)-H$

Which of the following combinations amongst the four Fischer projections represents the enantiomers?

The Fischer projection of $D$-erythrose is shown below.
$D$-Erythrose and its isomers are listed as $P$,$Q$,$R$,and $S$ in Column-$I$. Choose the correct relationship of $P$,$Q$,$R$,and $S$ with $D$-erythrose from Column-$II$.
Column-$I$:
$P$: $CHO-C(OH)(H)-C(OH)(H)-CH_2OH$ (rotated)
$Q$: $CHO-C(H)(OH)-C(OH)(H)-CH_2OH$
$R$: $CHO-C(OH)(H)-C(H)(OH)-CH_2OH$
$S$: $CHO-C(H)(OH)-C(H)(OH)-CH_2OH$ (enantiomer)
Column-$II$:
$1$. Diastereomer
$2$. Identical
$3$. Enantiomer