I think Option E is right.

The premise of the argument says that hazardous waste was 90 per production worker before and now It has reduced to 40 per per-production worker.Option E says number of production workers for the same task has remained the same. So we can conclude the same

Nevertheless, Option A is strong contender.

In order for the conclusion to hold good, the amount of hazardous waste generated by the Passanger Jet, on the whole, should have reduced by atleast half of that in 1994. The premise shows that the amount of waste generated per production worker has reduced by half. Now if the number of production workers had been substantially more than that in 1994, the total amount of hazardous waste will still be more @ 40/production worker. So it is important to note that the conclusion will hold good only when the increase in number of production workers, if any, is not substantial. Hence Answer choice E

I agree with above comments.

As statement state "per worker" it assumes that the number of workers did not change significantly