Approving (or sealing) work means accepting professional responsibility for it. NPPE practice guidance stresses that a professional must not rely blindly on work prepared by others outside their direct supervision. To accept responsibility, the professional must perform a level of review and verification sufficient to be confident the work meets the applicable standard of care, is fit for purpose, and complies with relevant codes and requirements. This requires a thorough review (C), which may include checking key assumptions, inputs, methods, calculations, and outputs, and obtaining clarification or additional information where needed. It does not necessarily require redoing every calculation (B) in full, but the review must be substantive. Interviewing everyone involved (A) is not required and is not a substitute for technical verification. A cursory review (D) is inadequate to support responsible approval. Therefore, C is correct.