In polluted environments, dolphins gradually accumulated toxins in their body fat, and the larger the dolphin the more accumulated toxin...
GMAT Critical Reasoning : (CR) Questions
In polluted environments, dolphins gradually accumulated toxins in their body fat, and the larger the dolphin the more accumulated toxin it can tolerate. Nearly 80 percent of the toxins a female dolphin has accumulated pass into the fat-rich milk her nursing calf ingests. Therefore, the unusually high mortality rate among dolphin calves in the industrially contaminated waters along Florida's Gulf Coast is probably the result of their being poisoned by their mother's milk.
Which of the following, if true, most strengthens the argument?
Passage Analysis:
| Text from Passage | Analysis |
| In polluted environments, dolphins gradually accumulated toxins in their body fat, and the larger the dolphin the more accumulated toxin it can tolerate. |
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| Nearly 80 percent of the toxins a female dolphin has accumulated pass into the fat-rich milk her nursing calf ingests. |
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| Therefore, the unusually high mortality rate among dolphin calves in the industrially contaminated waters along Florida's Gulf Coast is probably the result of their being poisoned by their mother's milk. |
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Argument Flow:
The argument starts with general facts about dolphins and toxins, then shows how toxins transfer to babies, and finally applies this to explain a specific problem in Florida
Main Conclusion:
The high death rate among baby dolphins in Florida's polluted coastal waters is probably caused by toxin poisoning from their mother's milk
Logical Structure:
The argument uses a cause-and-effect chain: polluted environment → toxins accumulate in mother dolphins → toxins transfer through milk → baby dolphins get poisoned → high mortality rate in Florida
Prethinking:
Question type:
Strengthen - We need to find information that makes the conclusion more believable. The conclusion is that high calf mortality in Florida's Gulf Coast is probably due to poisoning from mother's milk.
Precision of Claims
The argument makes specific quantitative claims (80% toxin transfer, unusually high mortality rate) and connects toxin accumulation to calf deaths through a causal chain.
Strategy
To strengthen this argument, we need information that either: (1) confirms the toxin transfer is actually harmful to calves, (2) rules out alternative explanations for the high mortality, (3) shows the toxin levels are particularly dangerous in this specific location, or (4) demonstrates that calves are especially vulnerable to these toxins compared to adults.
This choice tells us that firstborn calves whose mothers died before weaning had the highest survival rates in the Florida Gulf Coast area. This strongly supports our conclusion because it shows that when calves stop receiving mother's milk (the suspected source of toxins), they actually survive better. The fact that this applies specifically to firstborn calves is crucial because firstborn calves would receive the most concentrated dose of toxins since their mothers haven't previously transferred toxins to other offspring. This creates a direct link between stopping milk consumption and improved survival, which strengthens the argument that mother's milk is indeed the cause of high mortality.
This choice compares the toxin accumulation rate of adult dolphins in Florida to those in other similarly polluted areas, finding no difference. However, this doesn't strengthen our argument about calf mortality. The issue isn't whether Florida's adult dolphins accumulate toxins faster than elsewhere, but whether the toxins they do accumulate are causing calf deaths through milk transfer. Even if accumulation rates are similar elsewhere, we don't know about calf mortality rates in those other areas, so this comparison doesn't help establish causation.
This states that among calves born in the Florida area, mortality is highest among those with living siblings. This actually weakens rather than strengthens our argument. If toxin transfer through milk were the primary cause of death, we might expect firstborn calves (who receive the most concentrated toxins) to have higher mortality rates, not calves with siblings. This choice suggests other factors might be at play.
This tells us that dolphins accumulate toxins more slowly as they age compared to when they were young. While this might explain why adults can tolerate toxins better, it doesn't directly address whether mother's milk is causing calf mortality in Florida. The information about age-related accumulation rates doesn't strengthen the connection between nursing and calf deaths.
This provides general information that dolphins have higher body fat proportions than land mammals. Since toxins accumulate in body fat, this might explain why marine mammals are more susceptible to toxin accumulation overall. However, this doesn't specifically strengthen the argument about Florida calf mortality being caused by toxin transfer through nursing. It's too general and doesn't address the specific causal relationship we're trying to establish.