The set of positive integers under the operation of ordinary multiplication is:

(A) not a monoid (B) not a group

(C) a group (D) an Abelian group

B> Not a group but monoid because the inverse element does not exist as they will not be integers

eg: the multiplicative inverse of 3 will be 1/3 which donot closed under positive integer

Ooh sorry sorry Dharmendra Lodhi