Difficulty: Medium

Average Score: 70%

Oysters absorb the chemicals that are present in the water they live in; therefore, examining the chemical concentrations in oyster tissue can indicate levels of industrial pollution. However, the results of such examination must be interpreted carefully. For example, high levels of cadmium in oysters along the West Coast of the United States can be attributed not to pollution by industry, but to upwelling of deep ocean water, which contains more cadmium than surface ocean water.

The passage is primarily concerned with

Rationale

advising caution in drawing conclusions regarding the presence of pollutants in the tissue of oysters.

The passage emphasizes the need for careful interpretation of chemical concentrations in oyster tissue, particularly in relation to cadmium levels, which may not solely indicate industrial pollution. This caution stems from the influence of natural oceanic processes, such as upwelling, which can alter chemical concentrations independent of human activity.

A (suggesting a method for determining the level of pollution in ocean water) YOUR ANSWER

While the passage discusses the examination of oyster tissue as a means to assess pollution levels, it does not propose a specific method for this determination. Instead, it focuses on the complexities and potential misinterpretations associated with such assessments.

B (pointing out a flaw in the reasoning of scientists who study the concentration of chemicals in ocean water) YOUR ANSWER

The passage does highlight a misunderstanding regarding the source of cadmium levels but does not directly critique the reasoning of scientists. Rather, it underscores the importance of context when interpreting data, which is a broader caution than merely identifying flaws in reasoning.

C (warning of the danger to oysters of cadmium in ocean water) YOUR ANSWER

Although cadmium is mentioned, the passage does not primarily focus on the dangers it poses to oysters. Instead, it elaborates on the sources of cadmium and the implications for pollution assessment, rather than issuing a warning about its toxicity to oysters.

D (contrasting the harm done by industrial pollution with the effects of pollution from other sources) YOUR ANSWER

The passage does not engage in a direct comparison between industrial pollution and other sources of pollution. Instead, it emphasizes the natural origins of certain chemical concentrations, specifically cadmium, without framing it as a contrast to industrial pollution.

Conclusion

The essence of the passage is to advise caution in interpreting the presence of pollutants in oyster tissues. It suggests that while oysters can reflect environmental chemical concentrations, one must consider various factors that influence these levels, particularly natural processes like upwelling. This understanding is crucial for accurate assessments of environmental health and pollution.

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