why not A

Let's diagram: "A book tour will be successful if it is well publicized and the author is an established writer." P1: WP & EW ==> BTS not BTS ==> not WP or not EW "Julia is an established writer, and her book tour was successful." P2: EW & BTS "So her book tour must have been well publicized." C: WP The argument erroneously reasons by using the necessary condition "BTS" and one of the two sufficient conditions "EW" to conclude the other sufficient condition "WP." We cannot use a necessary condition to conclude anything, let alone to conclude a sufficient condition. Let's diagram (A): "This recipe will turn out only if one follows it exactly and uses high-quality ingredients." P1: RTO ==> FE & HQI not FE or not HQI ==> not RTO "Arthur followed the recipe exactly and it turned out." P2: FE & RTO "Thus, Arthur must have used high-quality ingredients." C: HQI Unlike the first stimulus, we have two necessary conditions and only one sufficient condition. Whereas the stimulus and answer choice (C) both have two sufficient conditions and one necessary condition along with the same reasoning. Hope that clears things up!

Great explanation- thanks!

How did you know that they are necessary conditions? Is it the qualifier?

@MJA7, happy you liked Naz's explanation! Let us know if you have any other questions! @heidiz, We know that they're the necessary conditions because they're on the right side of the conditional chain. IF X, then Y X - >Y X is the sufficient condition, and Y is the necessary condition. The stimulus's diagram: WP + EW - >BTS BTS is the necessary condition Julia: EW and BTS C: WP The argument erroneously takes one sufficient condition and the necessary condition to conclude the other sufficient condition (C)'s diagram: KS + Watered more than twice weekly - >they'll die they'll die is the necessary condition Cactus: KS and dead C: watered more than twice weekly Just as in the stimulus, (C) makes the same error of taking one of the sufficient conditions and the necessary condition and concluding the other sufficient condition. Thus, (C) is the correct answer choice. Does this make sense? Let us know if you have any more questions!

Thanks @ravi, was it the wording that let you know what was on the right and what was on the left?