Right answer is (a) a*b=b*a
The explanation: A binary operation ‘*’ defined on a set A is said to be commutative only if a*b=b*a, ∀a, b∈A.
If (a*b)*c=a*(b*c), then the operation is said to associative ∀ a, b∈ A.
If (b ο c)*a=(b*a) ο (c*a), then the operation is said to be distributive ∀ a, b, c ∈ A.