Consider the systems, each consisting of m linear equations in n variables.

I. If m < n, then all such systems have a solution II. If m > n, then none of these systems has a solution III. If m = n, then there exists a system which has a solution

Which one of the following is CORRECT?

A | I, II and III are true |

B | Only II and III are true |

C | Only III is true |

D | None of them is true |