Final answer:
C) When the group operation is commutative. A group in mathematics consists of a set of elements with an operation and satisfies certain properties. An abelian group is a group in which the operation is commutative.
Step-by-step explanation:
A group in mathematics is a set of elements with an operation that satisfies certain properties. Specifically, a group consists of a set of elements, an operation (such as addition or multiplication), and four properties: closure, associativity, identity element, and invertibility.
For example, the set of integers under addition form a group because the operation of addition is closed, associative, there is an identity element (zero), and each element has an inverse (the negative).
An abelian group, also known as a commutative group, is a group in which the operation is commutative. This means that for any two elements a and b in the group, a*b = b*a.
So, the correct answer to the question is C) When the group operation is commutative.