本题应该weaken的是:it is argued that PRP contracts increase worker productivity
即不是PRP->提高productivity
D:Many firms in the metalworking industry have modernized production equipment in the last five years, and most of these introduced PRP contracts at the same time. 是说很多公司5年前引入了现代化的设备,同时引入了PRP,到底是谁导致了productivity很难说
E:In firms in the metalworking industry where PRP contracts are in place, the average take-home pay is 15 percent higher than it is in those firms where workers have more traditional contracts.有PRP的公司,员工工资高