2021 CSAT — Q4
Passage
Researchers were able to use stem cells to gauge the neurotoxic effects of the environmental pollutant Bisphenol A (BPA). They used a combination of biochemical and cell-based assays to examine the gene expression profile during the differentiation of mouse embryonic stem cells upon treatment with BPA, a compound known to cause heart diseases, diabetes, and developmental abnormalities in humans. They were able to detect and measure BPA toxicity towards the proper specification of primary germ layers, such as endoderm and ectoderm, and the establishment of neural progenitor cells.
On the basis of the passage given above, the following assumptions have been made:
-
BPA may alter embryonic development in vivo.
-
Biochemical and cell-based assays are useful in finding out treatments for pollution-induced diseases.
-
Embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants.
Which of the above assumptions are valid?
Thinking pathway
Locate. This is a valid-assumption question — find the unstated premise the argument needs. Push each statement through the fit check and keep only what stays inside the passage’s actual things, its stated cause-and-effect, and its level of certainty. The passage: researchers used stem cells “to gauge the neurotoxic effects” of BPA; BPA is “known to cause heart diseases, diabetes, and developmental abnormalities in humans”; they “detect and measure BPA toxicity towards the proper specification of primary germ layers… and the establishment of neural progenitor cells.”
Test (boundary test + negation). St1 — “BPA may alter embryonic development in vivo.” The passage states developmental abnormalities and germ-layer/neural-progenitor disruption; the hedged “may alter” sits at or below the passage’s strength and inside its entities. VALID. St3 — “embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants.” That is literally what the researchers did — used stem cells to gauge a pollutant’s effects. VALID. St2 — “assays are useful in finding out treatments.” The passage uses the assays to detect and measure toxicity, never to develop therapy; “treatments” re-routes the assays’ function to a purpose the text does not state. INVALID — it invents a use the passage never states.
Eliminate by anatomy. (a)/(b)/(d) all seat St2 — a claim the passage never makes: a detection-and- measurement tool misread as a treatment-finding tool. The transferable rule: an assumption that changes what a stated method is for (diagnosis → therapy) has left the passage’s cause-and-effect even if it sounds helpful. St1 and St3 keep the method’s stated purpose; St2 invents a new one. Key: (c).
Evidence in the text
Statement 1 — BPA is “a compound known to cause heart diseases, diabetes, and developmental abnormalities in humans,” and the study measured “BPA toxicity towards the proper specification of primary germ layers, such as endoderm and ectoderm”: the hedged “may alter embryonic development” stays inside the text (developmental abnormalities + germ-layer disruption) → VALID. Statement 3 — the researchers “use[d] stem cells to gauge the neurotoxic effects of the environmental pollutant”: using embryonic stem cells as a model to evaluate a pollutant’s physiological effects is the study’s own design → VALID. Statement 2 fires the MECHANISM/ENTITY boundary — the assays are used to DETECT and MEASURE toxicity, never to “find treatments”; “treatments for pollution-induced diseases” re-routes the tool’s purpose to therapy, a channel the passage never states → INVALID. → (c).
Worked rationale
The study uses embryonic stem cells plus biochemical/cell-based assays to detect and measure the toxicity of the pollutant BPA — a compound known to cause developmental abnormalities — on germ-layer specification and neural progenitor cells.
- St1 is a hedged restatement of the documented developmental/germ-layer harm: BPA may alter embryonic development. Valid.
- St3 restates the study’s design: stem cells as a model to evaluate a pollutant’s effects. Valid.
- St2 converts a toxicity-detection tool into a treatment-finding tool — a purpose the passage never assigns. Invalid.
Answer: (c) 1 and 3 only.
Why the other options miss
- A a claim the passage never makes: keeps the valid St1 but accepts St2’s leap from detecting toxicity to finding treatments, and drops the valid St3.
- B a claim the passage never makes: right on St3 but again seats the treatment-finding overreach of St2 while dropping St1.
- D a claim the passage never makes: the “accept everything” trap — adds St2’s unstated therapeutic purpose to the two genuinely valid assumptions.
Specialist insight
The single discriminating line is what the assays are for. The passage uses them to “detect and measure BPA toxicity” — pure diagnosis. St2 says they help “find treatments,” which is therapy. That is a MECHANISM-boundary crossing: same tool, silently re-pointed at a different job. The student is pulled to St2 because “assays help fight pollution-induced disease” is a comforting, plausible sentence — but plausibility is not the test; staying inside the passage’s stated purpose is. St1 (hedged harm) and St3 (the study’s actual model) both stay inside it.
The assays only detect and measure toxicity; St2 re-points them at "finding treatments," a purpose the passage never states, so only St1 and St3 survive — (c).