Answer is D
1)closure: $\forall a,b \in Q , a*b \in Q$, so closure Satisfied.
2)Associativity : All closed groups under multiplication satisfies Associativity,so associativity satisfied.
3)e=1 , identity element exists.
4)for $0 \in Q$ , inverse does not exist.
So, $(Q,*)$ is a monoid