In a group (G , .) is said to be abelian if
(a*b) =(b*a) ∀a,b ∈G
∴(ab)-1 = (b--1a-1)............(1)
Given ,(ab)-1= a-1b-1 ..........(2)
from (1) and (2) we can write
a-1b-1 = b-1 a-1
we can also write it as
ab=ba
Hence,Option(B)Abelian Group is the correct choice.