Question

a researcher performed an experiment in which he exposed young corn plants to a harmless, radioactive form of carbon dioxide gas containing carbon-14 instead of carbon-12. he then began feeding corn produced by the plants to a small group of goats. after several weeks, the researcher took blood and tissue samples from the goats. he was able to detect increased concentrations of carbon-14 in the goats lipids, proteins, carbohydrates, and dna. which statement best explains the researchers findings?

a. like the corn plants, the goats experienced prolonged exposure to carbon dioxide gas containing carbon-14.

b. carbon atoms found in the sugar molecules of the corn were used by the goats bodies to form other large molecules.

c. eating corn containing radioactive carbon-14 caused many of the goats other carbon atoms to become radioactive.

d. uptake of radioactive carbon dioxide gas caused carbon atoms to be found in places they wouldnt normally be found.

Explanation:

• Option A: Goats were fed corn, not exposed to carbon - 14 gas, so A is wrong.
• Option B: Corn uses carbon - 14 from $CO_2$ to make sugars (photosynthesis). Goats eat the corn, and the carbon from corn's sugars is used to build other macromolecules (lipids, proteins, DNA) in goats. This matches the detection of carbon - 14 in goat's macromolecules.
• Option C: Eating radioactive corn doesn't make other carbon atoms radioactive; it's the carbon - 14 from corn being incorporated, so C is wrong.
• Option D: The finding is about carbon - 14 from corn being used in goat's molecules, not about carbon in abnormal places, so D is wrong.

Answer:

B. Carbon atoms found in the sugar molecules of the corn were used by the goats’ bodies to form other large molecules.