Which keyword is used to enforce sharing rules in Apex web service methods?

The keyword "with sharing" is used in Apex to enforce the sharing rules defined in Salesforce. When an Apex class is declared with this keyword, it ensures that the code respects the record-level access permissions of the current user. This means that if a user does not have access to certain records due to sharing settings, those records will not be accessible within the scope of the code execution.

This is particularly important in web service methods, as it ensures that sensitive data is not inadvertently exposed to users who do not have the appropriate permissions to view it. By utilizing "with sharing," developers can maintain data security and compliance with business rules regarding data visibility.

In contrast, other keywords like "without sharing" would allow the code to bypass these sharing rules, potentially leading to unauthorized data access. The options that do not directly pertain to Apex sharing rules do not serve the same function as "with sharing." This makes "with sharing" the appropriate choice for enforcing sharing rules in Apex web service methods.