The conclusion of the argument is: oil rigs had no adverse effect on sea-bottom animals.
Why? A study compared the sea-bottom communities near rigs with those located in control sites several miles from any rig and found no significant differences.
Answer choice (B) states: "The discharge of oil from offshore oil rigs typically occurs at the surface of the water, and currents often carry the oil considerable distances before it settles on the ocean floor."
Thus, the areas the study was comparing were not accurate samples of areas that were contaminated by oil rigs and control groups. If answer choice (B) were true, the sea-bottom communities near rigs would not be contaminated since the oil from offshore oil rigs occur at the surface of the water rather than on the sea bottom; furthermore, the oil on the surface is carried considerable distances before it finally settles on the ocean floor.
Thus, even looking at sea-bottom communities only "several miles away" might not be accurate control sites, since those sites may or may not be contaminated depending on how far they are from the rigs and whether the oil from the surface of the water has finally settled to the ocean floor.
Thus, if answer choice (B) were true, then it would seriously weaken the researcher's conclusion since the study would be rendered ineffective.
Hope that clears things up! Please let us know if you have any other questions.
jstaffSeptember 14, 2018
I had a hard time deciding between B & C. Unfortunately I went with C because of the ' "no adverse effect" portion of the conclusion. What exactly makes C a poor answer choice? Thanks
OwenCFebruary 11, 2019
I am also unsure of why C was not correct.
KatherineFebruary 13, 2019
Hi @jstaff and @OwenC,
It looks like both of you are unsure why Answer C is not correct. Let’s take a look at that answer.
Answer C says that contamination of the ocean floor from sewage and industrial effluent does not result in the total destruction of sea animals, but instead reduces species diversity as well as density of animal life. If this passage were true, the scientists who performed the study should be looking for differences in species diversity and density between the sea-bottom communities near rigs versus those in control sites. However, the passage says that the scientists found “no significant differences†between the two communities. Even if true, this fact about the effect on contamination on sea-bottom animals would not weaken the researcher’s conclusion.
If the researchers had instead concluded that oil rigs had no adverse effect on sea-bottom animals after only finding that the contamination had not resulted in the total destruction of sea-bottom life than this answer would be correct. However, the passage says that the researchers found “no significant differences†between the communities, which presumably would include a study of species diversity and density.
For the reasons explained by Naz above, Answer B is correct. If Answer B were true, the researcher’s conclusion would be seriously weakened.
I hope this is helpful. Please reach out with other questions.
