\( \begin{array}{l}\text { Which of the following function declarations will } \\ \text { correctly pass an output stream to the function? } \\ \text { void display( ostream out); } \\ \text { void display( ofstream\& out); and void display( } \\ \text { ostream\& out); } \\ \text { void distlay( ofstream out); } \\ \text { void display( ostream\& out); } \\ \text { void display( ofstream\& out); }\end{array} \)

To correctly pass an output stream to a function in C++, you should pass the stream by reference. This approach avoids object slicing and ensures that the function can handle the stream polymorphically, especially when dealing with different kinds of output streams like `ostream` and `ofstream`. Let's evaluate each of the provided function declarations: 1. **`void display(ostream out);`** - **Incorrect**: This passes the `ostream` object by value, which can lead to slicing and inefficiency. 2. **`void display(ofstream& out);` and `void display(ostream& out);`** - **Correct**: Both functions pass the stream by reference, allowing for efficient and polymorphic handling of the stream. 3. **`void distlay(ofstream out);`** - **Incorrect**: Similar to the first option, this passes the `ofstream` object by value and also contains a typo in the function name (`distlay` instead of `display`). 4. **`void display(ostream& out);`** - **Correct**: This passes the `ostream` object by reference, which is appropriate. 5. **`void display(ofstream& out);`** - **Correct**: This passes the `ofstream` object by reference, which is appropriate. **Conclusion:** The correct declarations are those that pass the stream by reference. Specifically: - `void display(ofstream& out);` - `void display(ostream& out);` These declarations ensure that the output stream is passed efficiently and correctly, allowing the function to manipulate the stream as intended. **Example:** ```cpp #include #include void display(std::ostream& out) { out << "Displaying output stream correctly passed by reference." << std::endl; } int main() { // Using with std::cout display(std::cout); // Using with a file stream std::ofstream file("output.txt"); if (file.is_open()) { display(file); file.close(); } return 0; } ``` In this example, the `display` function correctly handles both `std::cout` (an `ostream`) and a file stream (`ofstream`) by accepting them as references. **Final Answer:** Both the declarations taking an ofstream reference and an ostream reference, for example:  void display(ofstream& out);  void display(ostream& out);