Question

A subset of the additive group of real numbers which is not a sub group is

• A. (Q, +)
• B. (N, +)
• C. (Z, +)
• D. ({0}, +)

Answer 1

Answer: (B)

(N, +)

Answer 2

In additive subgroup '0' is the identity element, but $0 \notin N$.
$\therefore$ Required set $(N,+)$ which is not subgroup.