Question: Why does this code _not_ compile?

1. The returned `fn` pointer and value need to be represented by another trait.
2. Closures are types, so they cannot be returned directly from a function.
3. Closures are types and can be returned only if the concrete trait is implemented.
4. Closures are represented by traits, so they cannot be a return type.

Answer: The correct answer of the above question is Option D:Closures are represented by traits, so they cannot be a return type.