It was clear that the small grocery was_____ people he   owed money to.   [ ]

A. at the expense of              

B. at the risk of    

C. in the way of                    

D. at the mercy of

放疗单位应设立放射防护和质量控制管理组织，放射肿瘤医师，医学物理人员和放射治疗技师等医技人员在各自的工作中实施防护和质量控制措施，并承担相应的责任。