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 diabetes, and heart diseases, cause 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: 1. BPA may alter embryonic development in vivo. 2. Biochemical and cell-based assays are useful in finding out treatments for pollution-induced diseases. 3. Embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants. Which of the above assumptions are valid?

Statement 1: "BPA may alter embryonic development in vivo." The passage states BPA is "a compound known to... cause developmental abnormalities in humans" and that researchers detected BPA toxicity towards "the proper specification of primary germ layers, such as endoderm and ectoderm, and the establishment of neural progenitor cells." These are fundamental processes of embryonic development. While the study uses stem cells (in vitro), the observed effects and the known properties of BPA strongly imply it could alter development in a living organism (in vivo). Thus, this is a valid assumption. Statement 2: "Biochemical and cell-based assays are useful in finding out treatments for pollution-induced diseases." The passage describes using these assays to "examine the gene expression profile" and "detect and measure BPA toxicity." The focus is on *evaluating* and *understanding* the toxic effects, not on *finding treatments*. The passage does not provide information to support this assumption. Statement 3: "Embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants." The passage explicitly states, "Researchers were able to use stem cells to gauge the neurotoxic effects of the environmental pollutant Bisphenol A (BPA)." This directly demonstrates the use of embryonic stem cells as a model to evaluate the biological (physiological) effects of a pollutant. Thus, this is a valid assumption. Based on the analysis, only statements 1 and 3 are valid assumptions. The final answer is C.