True :
C. The with sharing Keyword (Runtime Enforcement):
Declaring an Apex class with the with sharing keyword forces the code to respect the executing user’s record-level security (sharing rules, role hierarchy, OWD). If a sales manager calls an API or uses a component driven by this class, they will only be able to view or modify shipment records they have explicit access to, preventing accidental data leakage.

B. The System.runAs() Method (Testing Validation):
Security architectures are only as good as their tests. The System.runAs() method allows developers to write automated test classes that execute code from the perspective of a specific user or profile (e.g., a Sales Manager vs. a Standard User). This allows you to programmatically assert and prove to the IT team that your sharing logic works as intended and blocks unauthorized access before code hits production.

Analysis of the Incorrect Options
A. isShareable keyword: This does not exist in the Apex language.

D. isAccessible keyword: While Schema.sObjectType.Object.isAccessible() is a valid method used to check Object and Field-Level Security (CRUD/FLS), it is not a class-level keyword, and it does not govern record-level visibility (sharing). Furthermore, the option misspells it as "isAccessable."...

NB: IsAccessible: https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_sobject_describe.htm