Wrong flaw. (A) gives us two conditional statements. It then tries to chain them to draw a conclusion about all walls, but the first statement is only about stone walls, so they cannot be chained. The stimulus, meanwhile, features two sufficient conditions leading to the same necessary condition, with a conclusion stating that one sufficient condition leads to the other, so (A) doesn’t match.

Wrong flaw. (B) sets up a conditional relationship: if a play is performed before a different audience every time, then it will never get the same reaction twice. It then tries to show that the sufficient condition leads to the necessary condition. A play not being performed before the same audience every time is different from a play being performed to a different audience every time, however, so the conclusion doesn’t follow. The stimulus, meanwhile, features two sufficient conditions leading to the same necessary condition, so (B) doesn’t match.

(C) establishes two sufficient conditions leading to the same necessary condition: If a person is perfectly honest or morally upright, then they will always tell the truth. (C) then invalidly concludes that one of the sufficient conditions leads to the other (perfectly honest→morally upright). The stimulus also features two sufficient conditions leading to the same necessary condition, with a conclusion stating that one sufficient condition leads to the other, so (C) matches.

No flaw. (D) gives us a valid conditional chain: Productive→Soil Well Drained→Good Soil. It then validly concludes that if a garden does not have good soil, then it won’t be productive.

Wrong flaw. (E) gives us the following conditional chain: Healthful Diet→Well Balanced→Includes Fruits and Vegetables. It then concludes that if one does not eat fruits and vegetables, then they will not be healthy. This is flawed because this only proves that someone will not have a healthy diet, not that they won’t be healthy overall. The stimulus, however, features two sufficient conditions leading to the same necessary condition, with a conclusion stating that one sufficient condition leads to the other, so (E) doesn’t match.