"People who are red/green color-blind cannot distinguish between green and brown."
So: if you are red/green color-blind, then you cannot distinguish between green and brown.
P1: RGCB ==> not DBGB DBGB ==> not RGCB
"Gerald cannot distinguish between green and brown."
P2: not DBGB
"Therefore Gerald is red/green color-blind."
C: RGCB
As you can see, the passage uses the necessary condition, "not DBGB," to conclude the sufficient condition, "RGCB." A necessary condition will never give us any more information. Thus, this is argument is flawed since it is mistaking a necessary condition for a sufficient condition.
Our correct answer will have the exact same flaw in reasoning.
Answer choice (D) states:
"People who are color-blind cannot become airline pilots."
So: If you are color-blind, then you cannot become a pilot.
P1: CB ==> not BP BP ==> not CB
"Arthur is color-blind.
P2: CB
"Therefore, Arthur cannot become an airline pilot."
C: not BP
Answer choice (D) is a valid argument. We know that Arthur is "CB," and we know from "P1" that "CB" guarantees "not BP." So, we can validly conclude that Arthur cannot become an airline pilot.
Thus answer choice (D) does not closely parallel the reasoning in the argument presented in the passage.
Answer choice (B), on the other hand, closely parallels the reasoning in the argument presented in the passage.
"People who are suffering from sinusitis lose their sense of smell."
So: If you are suffering from sinusitis, then you lose your sense of smell.
P1: SS ==> LSS not LSS ==> not SS
"Mary has lost her sense of smell."
P2: LSS
"Therefore Mary is suffering from sinusitis."
C: SS
Just as with the argument in the passage, answer choice (B) uses a necessary condition, "LSS," to conclude a sufficient condition, "SS." So, answer choice (C), just like the passage, mistakes the necessary condition of the principle rule with the sufficient condition.
Hope that clears things up! Please let us know if you have any other questions.
