Recursive functions can be declared as inline, but it's important to understand the implications. While technically possible, inlining recursive functions can lead to code bloat and stack overflow errors, as each inlined call consumes stack space. The decision to inline recursive functions should be made judiciously based on the specific use case.

In a switch statement, the default label is used to specify a block of code that is executed when none of the case labels match the switch expression. It serves as a fallback option when no specific case is satisfied, allowing you to handle unexpected or unspecified input gracefully.

In C++, global variables are declared outside of any functions or classes, typically before the main() function. They have global scope, meaning they can be accessed from anywhere within the program, making them accessible to all functions.

Grace can use the "Switch" statement to process different keys in her game. The "Switch" statement is well-suited for scenarios where different actions need to be taken based on the specific value (key) provided, making it ideal for handling player actions.

Inline functions can significantly help in a real-time system by reducing function call overhead. They do this by effectively replacing function calls with the actual function code, thus eliminating the overhead of pushing and popping stack frames. This optimization is critical for minimizing delays and ensuring timely responses in real-time systems.

The * (Multiplication) operator has the highest precedence in C++. This means that it is evaluated before other operators when multiple operators are used in an expression. Understanding operator precedence is crucial for writing correct and efficient C++ code.

The compiler may choose not to inline a function if it's too complex, as inlining large functions can lead to increased code size and reduced performance. Other factors such as optimization settings, memory constraints, and compiler versions also play a role in the decision. The 'inline' keyword is a hint to the compiler, and it may still choose not to inline based on these factors.

Anna should consider making the function inline. Inlining a function means that instead of calling the function, the compiler will insert the function's code directly at the call site. This can eliminate the overhead of function calls and improve performance, especially when the function is small and called frequently in a loop. However, inlining should be used judiciously as it can lead to code bloat if overused.

In C# and many other programming languages, the keyword void is used to declare a function that doesn't return any value. Functions declared with void indicate that they perform a task but don't produce a result that needs to be returned.

The correct keyword in this context is #if. It is used in preprocessor directives to conditionally compile blocks of code based on compiler settings or predefined macros.