Wrong flaw. This establishes a disjunctive necessary condition, meaning at least one of the two conditions must be met in order for a person to play the piano well. (A)’s flaw is assuming that both conditions must have been met since Paul plays well. The stimulus doesn’t provide such a condition—it mistakes two separate necessary conditions for sufficient ones.

This mistakes a necessary condition for a sufficient one. Bilingualism is required in order to become an effective foreign language teacher, but Professor Yessios may fail to be one for any number of other reasons.

No flaw. This interprets a necessary condition properly. Since completing an apprenticeship is necessary for becoming a licensed plumber, it follows that Martin—a licensed plumber—must have met that requirement.

Wrong flaw. This is directionally correct in how it interprets a necessary condition, but fails to establish that Leroux is an effective mayor of a major industrial seaport. The stimulus, in contrast, is not directionally correct since it mistakes a necessary condition for a sufficient one.

No flaw. This properly applies a necessary condition. Since using fresh vegetables is required for making a delicious vegetable soup, it follows that this delicious vegetable soup must have used fresh vegetables.