The correct answer is A. Multiplying number of rows and number of columns.
A two-dimensional array is an array that has two indices, one for the row and one for the column. The number of elements in a two-dimensional array is therefore the product of the number of rows and the number of columns.
For example, if a two-dimensional array has 3 rows and 4 columns, then it will have 12 elements. This is because each row has 4 elements, and there are 3 rows.
Option B is incorrect because it adds the number of rows and the number of columns. This will not give the correct number of elements in the array.
Option C is incorrect because it multiplies the number of rows and the number of rows. This will not give the correct number of elements in the array.
Option D is incorrect because it adds the number of columns and the number of columns. This will not give the correct number of elements in the array.