Chemists find _____ to detect and measure the amount of chlorine in any given water supply.
A.are easyB.easilyC.it easyD.how easily在线课程C
解析：
后面的the amount of chlorine in any given water supply.虽然并不重要，但其过去分词given的用法和supply作为名词的使用以及名词water作为定语的使用特点，都值得注意。