What is the order of a matrix?

The order of a matrix is given by the indicated product m x n, where 'm' indicates the number of rows and 'n' the number of columns.
The order of a matrix is given by the indicated sum m + n, where 'm' indicates the number of rows and 'n' the number of columns.
The order of a matrix is given by the indicated product m x n, where 'm' indicates the number of columns and 'n' the number of rows.
The order of a matrix is given by the indicated sum m + n, where 'm' indicates the number of columns and 'n' the number of rows.
a) I and II are correct.
b) II and III are correct.
c) I and III are correct.
d) I and IV are correct.