单选题 The private detective, having received new information from a confidential source, narrowed down the ______ of his enquiry into the case.
A. aspect B. sphere C. dimension D. scope

【正确答案】 D
【答案解析】scope范围。句意：由于通过秘密途径获得新的线索，那名私人侦探缩小了调查此案的范围。aspect方面，外表；sphere领域；dimension方面，重要性。