单选题 It is difficult to discern the sample that is on the slide unless the microscope is adjusted.

【正确答案】 C
【答案解析】画线词discern:分辨,识别。与C.determine“分辨,确定”为近义词。辨义:A.discard抛弃: B.arrange安排,安置;D.disagreement不一致,分歧。由分析可知答案为C。