Which of the following correctly deallocates memory allocated for an array in C++?delete ptr;delete[] ptr;free(ptr);delete array ptr;

The correct way to deallocate memory allocated for an array in C++ is by using delete[] ptr;.

Here's why:

1. delete ptr; - This is used to delete memory allocated for a single object, not an array. If used on an array, it will only delete the first element, leading to a memory leak.

2. delete[] ptr; - This is the correct way to delete memory allocated for an array in C++. It deletes the entire array and deallocates the memory.

3. free(ptr); - This is a C language function, not C++. While it can deallocate memory, it doesn't call the destructor for the object, which can lead to issues in C++.

4. delete array ptr; - This is not a valid syntax in C++. The correct syntax to delete an array is delete[] ptr;.