Which two are valid instantiations and initializations of a multi dimensional array?

This option represents a valid way to instantiate a multi-dimensional array (often called a jagged array). For example, `int[][] arr = new int[3][];` correctly declares a 2D array with 3 rows, where each row can later be assigned an array of variable length.

An invalid instantiation often involves specifying the second dimension without the first when using `new`, e.g., `int[][] arr = new int[][3];` which is syntactically incorrect.

An invalid declaration or instantiation could be incorrect placement of brackets like `int[3][4] arr;` or trying to combine dimension sizes with an initializer list in a way not supported by the language (e.g., `new int[2][3] { {1,2}, {3,4} }` in Java).

This option represents a valid way to instantiate a rectangular multi-dimensional array by specifying the size for all dimensions. For example, `int[][] arr = new int[2][3];` correctly creates a 2D array with 2 rows and 3 columns.

Invalid initializations can include assigning an initializer list directly to an inner array without `new int[]`, e.g., `arr[0] = {1,2};`, or incorrect syntax for creating anonymous arrays.