one question, 3x.

many of the presidents and prime ministers who have had the most successful foreign policies had no prior experience in foreign affairs when they assumed office. although scholars and diplomats in the sacrosanct inner circle of international affairs would have us think otherwise, anyone with an acute political sense, a disciplined temperament, and a highly developed ability to absorb and retain information can quickly learn to conduct a successful foreign policy. in fact, prior experience alone will be of little value to a foreign policymaker who lacks all three of these traits.

the correct answer is : prior experience in foreign affairs is neither a sufficient nor a necessary condition for a president or prime minister to have a successful foreign policy.

and another answer is prior experience in foreign affairs is a necessary but not sufficient condition for a president or prime minister to have a successful foreign policy.

i just wondering foreign affairs is a necessary condition, it means that S-->N, N can't be  deduce to S.

so, here why the latter one is the wrong one?

Thanks