Canadian mining company Bre-X had soil samples from its Busa

[BTGmoderatorAT]

Canadian mining company Bre-X had soil samples from its Busang project examined for gold content in 1992. The positive news of gold being present attracted a range of investors - from unsophisticated individuals to saavy mining professionals - to invest in the Busang project. After years of successful promotion, the truth about this worthless property slowly emerged early in 1997 and drove Bre-X stock prices nearly to zero. A repeat analysis of the soil in 1997 indicated very low gold content. Thus the methods used to determine the gold content in 1992 must have been inaccurate.

Which of the following is an assumption on which the argument depends?

(A) The gold content of the soil in Busang was much lower in 1997 than it was in 1992.
(B) After 1992, Bre-X was not mining in the same areas of Busang that the sample was taken from.
(C) The methods used to assess gold content of the soil samples in 1992 were different from those generally used during that time.
(D) Bre-X did not have soil samples from any other Busang property examined for gold content.
(E) Gold was not added to the soil samples collected by Bre-X before the samples were examined.

What's the best approach to determine the answer? Can any experts help?

[DavidG@VeritasPrep]

Canadian mining company Bre-X had soil samples from its Busang project examined for gold content in 1992. The positive news of gold being present attracted a range of investors - from unsophisticated individuals to saavy mining professionals - to invest in the Busang project. After years of successful promotion, the truth about this worthless property slowly emerged early in 1997 and drove Bre-X stock prices nearly to zero. A repeat analysis of the soil in 1997 indicated very low gold content. Thus the methods used to determine the gold content in 1992 must have been inaccurate.

Which of the following is an assumption on which the argument depends?

(A) The gold content of the soil in Busang was much lower in 1997 than it was in 1992.
(B) After 1992, Bre-X was not mining in the same areas of Busang that the sample was taken from.
(C) The methods used to assess gold content of the soil samples in 1992 were different from those generally used during that time.
(D) Bre-X did not have soil samples from any other Busang property examined for gold content.
(E) Gold was not added to the soil samples collected by Bre-X before the samples were examined.

What's the best approach to determine the answer? Can any experts help?

Try negation. The correct answer, when negated, should undermine the argument.

E negated: Gold WAS added to the soil samples collected by Bre-X before the samples were examined.

Well, if gold was added to the samples, then the technology detecting gold wasn't flawed at all. The problem wasn't faulty sample analysis. It was that the sample had, in effect, been tampered with. Because E, when negated, undermines the argument, we know it's the correct answer.