Question

Which one of the following is not true ?

• A. Identity element in a group is unique.
• B. Inverse of an element in a group is unique
• C. Fourth roots of unity form an additive abelian group.
• D. Cancellation laws hold in a group.

Answer 1

Answer: (C)

Fourth roots of unity form an additive abelian group.

Answer 2

Fourth roots of unity form an additive abelian group is not true because $0$ is not exist.