Which statement can a developer use to throw a custom exception?

A developer can throw a custom exception in Salesforce by using the syntax that properly instantiates the exception object. The correct way to create and throw a custom exception is by using the new keyword followed by the name of the exception class and parentheses to indicate that you are creating a new instance of that exception. Additionally, a custom exception can accept a message that describes the specific problem, which can be useful for debugging and logging purposes.

In the correct answer, the instantiation includes a message "problem occurred," which is passed to the constructor of the RecordNotFoundException class. This provides context for the exception being thrown, allowing downstream code or the logged error to better understand what went wrong.

Using the other formats presented either lacks the necessary instantiation of the exception object or tries to call the constructor without the new keyword, which wouldn’t correctly create an instance of the exception. This is why the correct answer is valid, ensuring that the developer adheres to the proper exception handling standards in the Salesforce platform.