In which business object do you set whether the supplier must provide a quality certificate...

The requirement for a supplier to provide a quality certificate and its type is configured in:

Quality Info Record: Procurement (D): In the quality info record (transaction QI01), you set the "Certificate Required" indicator and specify the "Certificate Type" (e.g., "ISO 9001") under the "Certificate Data" section. This links the requirement to a specific material-supplier combination, enforced during GR (SPRO > QM > Quality Inspection > Quality Info Record).

Purchase Order (A): POs inherit certificate settings from the quality info record, not define them.

Material Master (B): The QM view defines inspection types, not certificate requirements or types.

Business Partner (C): Supplier master data lacks QM-specific certificate settings.

Thus, "Quality info record: Procurement" is the correct answer.References: SAP Help Portal - "Quality Info Record in QM"; SAP S/4HANA QM User Guide - "Certificate Management".