The main function in a Dart application is declared as void main() {}. To make it asynchronous, modify it to ____ main() async {}.

To make the main function in a Dart application asynchronous, modify it by adding the 'async' keyword, resulting in 'async main() {}'. This modification allows the use of asynchronous operations within the main function, enabling tasks like asynchronous I/O or handling Future objects. The 'async' keyword is crucial for writing Dart applications that efficiently handle asynchronous code, improving responsiveness and concurrency in Dart programs.