Creating new CI classes is a high-impact configuration activity and must follow strict Data Foundations and CSDM-aligned best practices to avoid long-term technical debt and upgrade risk.

Option B is a recommended first step. Before creating any new CI class, administrators should install or update the CMDB CI Class Models Store application and verify whether an appropriate class already exists. ServiceNow frequently delivers new CI classes through updates and class model packages, and duplicating an existing or planned class can lead to fragmentation and governance issues.

Option C is also correct. When a new class is truly required, it should be added under an appropriate parent class to inherit attributes, behaviors, and discovery patterns. For an IoT Sensor, this might be under a hardware or device-related parent class, ensuring consistency and minimizing customization.

Option A is incorrect and dangerous—deleting unused classes can break dependencies and historical data. Option D is also discouraged; modifying existing classes to repurpose them violates upgrade-safe design principles and can negatively impact discovery, integrations, and reporting.

By verifying existing models first and extending the class hierarchy correctly, organizations maintain a clean, scalable, and upgrade-safe CMDB.

Therefore, the correct answers are B and C.