Lockeport's commercial fishing boats use gill nets, which kill many of the netted fish, including some fish of endangered species. The fishing commission has proposed requiring the use of tent nets, which do not kill fish; boat crews would then throw back fish of endangered species. Profitable commercial fishing boats in similar areas have already switched over to tent nets. The proposal can therefore be implemented without economic harm to Lockeport's commercial fishing boat operators.

Which of the following, if true, casts the most serious doubt on the argument made for the proposal?

A. In places where the use of tent nets has been mandated, there are typically fewer commercial fishing boats in operation than there were before tent nets came into use.
B. Even when used properly, gill nets require many more repairs than do tent nets.
C. Recreational anglers in Lockeport catch more fish of endangered species than do commercial fishing boats.
D. The endangered species of fish in Lockeport's commercial fishing area did not become endangered as a result of the use of gill nets by fishing fleets.
E. The endangered species of fish caught by Lockeport's commercial fishing fleet are of no commercial value.

pls explain ur choice
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i think another way of describing option A is to say that fish boat operators virtually disappeared
when the new policy was introduced. So, if the operators withdraw their boats, we can easily infer
that the tent nets policy is far from being business friendly.
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Conclusion: (Marker = Therefore) Proposal (to use tent nets)can be implemented without economic harm.
Premise: Commercial fishing boats in similar areas have switched.
Weakness:

A: Ooooh.. weakens.
B: We are moving away from gill nets, remember? NO
C: Who cares
D: Who cares
E: Who cares

Look at A again:
Initially number was say 100
after the proposal the number is 50.
Has this caused economic harm? Possibly. Why else have the operators numbers gone down? They had a lot of profit so they went down???
It creates a doubt as to why the number went down. The number of boat operators is part of the argument and definitely within the scope of the argument.