The question asks us to pick the answer that most weakens the argument.
(C) says, "Certain chemicals that play a leading role in the way the VNO functions in animals in which it is highly developed do not appear to play a role in its functioning in humans."
(C) just informs us that the VNO functions differently in humans vs. in other animals. However, this does not mean that the VNO can't be a sensory organ in humans, so this doesn't weaken the argument. Thus, (C) is out.
(A) says, "It is not known whether the researchers succeeded in stimulating only VNO cells in the human subjects' noses."
It's possible that the researchers could have succeeded in stimulating other kinds of cells, which would mean that the smelling sensation could possibly have originated from something that isn't the VNO, such as the sense of smell. Thus, (A) weakens the argument, so it's the correct answer.
Does this answer make sense? Let us know if you have any other questions!
Anna20August 7, 2020
I have tried this question twice now, and am still not clear why A is correct or why is B incorrect here?
I'm not sure I am following why A is correct - It is not known whether the researchers succeeded in stimulating only VNO cells in the human subjects' noses - appears to wholly contradict the premise 'when researchers have been able to stimulate VNO cells in humans'. It was my understanding that the whole point was that the answers can't contradict the validity of the premise itself, but the logical structure / connection between the premise and conclusion?
