Match the following:

Animal	Excretory organ/Unit
$(a)$ Balanoglossus	$(i)$ Metanephridia
$(b)$ Leech	$(ii)$ Nephridia
$(c)$ Locust	$(iii)$ Flame cells
$(d)$ Liver fluke	$(iv)$ Absent
$(e)$ Sea urchin	$(v)$ Malpighian tubule
$(f)$ Pila	$(vi)$ Proboscis gland

(A) The correct matches are as follows:
$(a)$ Balanoglossus: $(vi)$ Proboscis gland
$(b)$ Leech: $(ii)$ Nephridia
$(c)$ Locust: $(v)$ Malpighian tubule
$(d)$ Liver fluke: $(iii)$ Flame cells
$(e)$ Sea urchin: $(iv)$ Absent (Excretion occurs via water vascular system)
$(f)$ Pila: $(i)$ Metanephridia (or renal organ)
Therefore,the correct sequence is $(a-vi, b-ii, c-v, d-iii, e-iv, f-i)$.