Prior to carrying out the experiment, Milgram explained his idea to a group of 39 psychiatrists and asked them to predict the average percentage of people in an ordinary population who would be willing to administer the highest shock level of 450 volts.(剑5, Test 1 passage 2)

　　● 分析：

　　本句的主句为“Milgram explained his idea to a group of 39 psychiatrists and asked them to predict the average percentage of people in an ordinary population.”; “Prior to carrying out the experiment”为时间状语，prior to相当于before; “who would be willing to administer the highest shock level of 450 volts.”为定语从句，做an ordinary population的定语，关系词为who。