The conclusion of the argument is: "the people who are concerned about damage to the seaside environment thus have nothing to fear from the tourist industry."
Why? Well, we know that people in the tourist industry know that excessive development of seaside areas by the industry damages the environment and that such development also hurts the tourist industry. We are told that people in the tourist industry would never knowingly do anything to damage the industry. Thus, they would never knowingly damage the seaside environment.
Answer choice (E) states: "The argument establishes that a certain state of affairs is likely and then treats that as evidence that the state of affairs is inevitable."
The topic of "inevitability" was never discussed in the stimulus, thus it could not be the flaw in the argument. The argument merely states that since the tourist industry is well aware that development of seaside areas is detrimental to the tourist industry and the tourist industry would never knowingly do anything to damage the industry, i.e. they would never knowingly damage the seaside environment, those who are concerned about damage to the seaside environment have nothing to fear from the tourist industry.
The flaw here is that just because the tourist industry would never knowingly hurt the industry, this does not eliminate the possibility that they might still unknowingly, i.e. unintentionally, damage the industry.
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