【题目】The level of __________ in the river was falling.
A. populationB. prescription
C. presentationD. pollution
在线课程【答案】D
【解析】
考查名词词义辨析。句意：河流的污染程度在下降。A. population人口；B. prescription处方；C. presentation呈现，展示；D. pollution 污染。根据本句的in the river可知，河流的污染程度，故选D。