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