Question: Does the `main` function compile? If so, why? If not, what do you need to change?

1. The code does not compile. `let` statements require a refutable pattern. Add `if` before `let`.
2. The code compiles. `let` statements sometimes require a refutable pattern.
3. The code does not compile. `let` statements requires an irrefutable pattern. Add `if` before `let`.
4. The code compiles. `let` do not require a refutable pattern.

Answer: The correct answer of the above question is Option C:The code does not compile. `let` statements requires an irrefutable pattern. Add `if` before `let`.