Determine whether or not the definition of $*$ given below gives a binary operation. In the event that $*$ is not a binary operation,give justification for this. On $Z^{+}$,define $*$ by $a * b = a - b$.

  • A
    Yes,it is a binary operation.
  • B
    No,it is not a binary operation because $a - b$ is not always in $Z^{+}$.
  • C
    No,it is not a binary operation because $a - b$ is not commutative.
  • D
    No,it is not a binary operation because $a - b$ is not associative.

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