`array[1][2]`

`array[2][3]`

`array[3][2]`

`array[2][1]`

`0`

`1`

`null`

`undefined`

`int[][] array = new int[5][5];`

`int array[][] = new int[][];`

`int[5][5] array = new int[][];`

`int array = new int[5][5];`

`matrix[0][0] = 10;`

`matrix[1][1] = 10;`

`matrix[0] = 10;`

`matrix = 10;`

`2`

`3`

`4`

`6`

A single `for` loop

A single `while` loop

Nested `for` loops

Recursive method calls

`3`

`2`

`5`

`6`

`int[][] grid = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};`

`int[][] grid = new int[1, 2, 3, 4, 5, 6, 7, 8, 9];`

`int[][] grid = new int[3][3]{1, 2, 3, 4, 5, 6, 7, 8, 9};`

`int[][] grid = new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9};`

A `NullPointerException` is thrown.

A `NegativeArraySizeException` is thrown.

An `ArrayIndexOutOfBoundsException` is thrown.

The program compiles and runs without any errors.

A 2D array can have rows of different lengths.

A 2D array must have all rows of the same length.

A 2D array is always square (same number of rows and columns).

A 2D array cannot contain primitive data types.