How can an Apex class be exposed as a SOAP web service?

To expose an Apex class as a SOAP web service, it is essential to use the appropriate keywords in the method definitions within the class. Specifically, marking methods with the 'webservice' keyword allows them to be called externally over SOAP. Additionally, these methods must also be defined as 'static' in order to be accessible without needing an instance of the class.

This combination of keywords indicates that the methods are intended to handle external requests and defines their behavior in the context of a SOAP web service. Therefore, option B accurately describes the necessary requirements for exposing an Apex class as a SOAP web service.