Match Column-$A$ with Column-$B$.

Column-$A$	Column-$B$
$(a)$ When source of sound and listener move towards wall.	$(i)$ Listener would hear a sound with same frequency as that of source.
$(b)$ When source of sound and listener move away from each other.	$(ii)$ Listener would hear a sound with frequency smaller than that of source.
	$(iii)$ Frequency of echo would be greater than that of source.

(A) For $(a)$,when both the source and the listener move towards a wall,the sound reflects off the wall. The wall acts as a secondary source. Since both are moving towards the reflecting surface,the frequency of the reflected sound (echo) heard by the listener increases due to the Doppler effect. Thus,$(a-iii)$.
For $(b)$,when the source and the listener move away from each other,the relative velocity between them increases,causing the observed frequency to decrease according to the Doppler effect formula $f' = f \left( \frac{v - v_L}{v + v_S} \right)$. Thus,$(b-ii)$.