Write the functions in brief in column $II$, appropriate to the structures given in column $I$.

Column - $I$	Column - $II$
$(A)$ Nictitating membrane	$(1)$ ..........
$(B)$ Tympanum	$(2)$ ..........
$(C)$ Copulatory pad	$(3)$ ..........

$(A)$ Nictitating membrane: It protects the eyes while the frog is in water.
$(B)$ Tympanum: It is a membranous structure located on either side of the eyes that receives sound signals.
$(C)$ Copulatory pad: It is a specialized structure located on the first digit of the forelimbs of male frogs, which helps in holding the female during copulation.