单选题 Another factor in the display of art objects (concerns their continued preservation). Because of the sensitivity of some of the materials (used in their creation), it is necessary to control (within narrow limits) the temperature, humidity, and lighting (which) they are exposed.
  • A. concerns their continued preservation
  • B. used in their creation
  • C. within narrow limits
  • D. which


【正确答案】 D
【答案解析】[解析] 此处考查的是词组expose to，意思是“使易受，使受”。引导定语从句时，to提前，用to which。