GMAT-9-16请教求解思路

sv2000

In response to mounting pubic concern, an airplane manufacturer implemented a program with the well-publicized goal of reducing by half the total yearly amount of hazardous waste generated by its passenger-jet division.  When the program began in 1994, the division’s hazardous waste output was 90 pounds per production worker; last year it was 40 pounds per production worker. Clearly, therefore, charges that the manufacturer’s program has not met its goal are false. Which of the following is an assumption on which the argument depends?

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yangsh

E,

volume=pounds/per worker  X  number of workers

the former declines form 90 to 40

but maybe the latter rises more than 3 times.

sv2000

题目不能很好的理解，能解释一下吗？谢谢