The number of optical isomers of lactic acid is

$A$ disymmetric object is one which is:

Ignoring specific markings,which of the following objects are chiral?
$(I)$ $A$ shoe
$(II)$ $A$ book
$(III)$ $A$ pencil
$(IV)$ $A$ pair of shoes (consider the pair as one object)
$(V)$ $A$ pair of scissors

Which of the following is optically active?

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

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

The number of chiral centers present in the given compound is: