Understanding 2D Arrays in C++

What is the correct syntax to declare a 2D array in C++ with 3 rows and 4 columns of integer type?

• `int arr[4][3];`

• `int arr[3][4];`

• `int arr(3)(4);`

• `int arr{3}{4};`

Which of the following correctly accesses the element in the second row and third column of a 2D array `arr`?

• `arr[3][2]`

• `arr[2][3]`

• `arr[1][2]`

• `arr[2][1]`

What is the index of the first element in a 2D array in C++?

• `[1][1]`

• `[0][1]`

• `[1][0]`

• `[0][0]`

Which of the following is a valid initialization of a 2D array in C++?

• `int arr[2][3] = {1, 2, 3}, {4, 5, 6};`

• `int arr[2][3] = {{1, 2, 3}, {4, 5, 6}};`

• `int arr[2][3] = [[1, 2, 3], [4, 5, 6]];`

• `int arr[2][3] = {(1, 2, 3), (4, 5, 6)};`

How many elements does a 2D array declared as `int arr[5][6]` contain in total?

• 11

• 25

• 30

• 36

What will be the value of `arr[1][2]` after the following initialization? ```cpp int arr[2][3] = {{10, 20, 30}, {40, 50, 60}}; ```

• 20

• 40

• 50

• 60

Which of the following nested loop structures correctly iterates through all elements of a 2D array `arr[3][4]`?

• `for(int i=0; i<4; i++) for(int j=0; j<3; j++)`

• `for(int i=1; i<=3; i++) for(int j=1; j<=4; j++)`

• `for(int i=0; i<3; i++) for(int j=0; j<4; j++)`

• `for(int i=0; i<=3; i++) for(int j=0; j<=4; j++)`

What happens when a 2D array in C++ is partially initialized, such as `int arr[2][3] = {{1, 2}, {4}};`?

• A compilation error occurs

• The uninitialized elements are set to garbage values

• The uninitialized elements are automatically set to 0

• The program crashes at runtime

Given the following code, what is the output? ```cpp int arr[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}; int sum = 0; for(int i = 0; i < 3; i++) sum += arr[i][i]; cout << sum; ```

• 12

• 15

• 45

• 9

Which of the following correctly declares a 2D array where the number of columns must be specified but the number of rows can be omitted?

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

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

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

• `int arr[2][4];` only