White noise consists of________ collections of sounds at different frequencies，such as the dull nois

White noise consists of________ collections of sounds at different frequencies，such as the dull noise of aircraft engines.
A. swift B. fierce C. random D. generous
【答案】C
【解析】
【详解】考查形容词词义辨析。句意：白噪音由不同频率的声音随机组合而成，例如飞机引擎的沉闷噪音。A. swift 快速的；B. fierce 凶猛的；C. random 随意的，随机的；D. generous 慷慨的。分析句子，根据后面提到的“例如飞机引擎的沉闷噪音”可知，白噪音是有不同频率的声音随机组合。故选C项。