If one has evidence that an act will benefit other people and performs that act to benefit them, then one will generally succeed in benefiting them. Which one of the following best illustrates the proposition above? ['Zachary hoped that psychotherapy could help his parents overcome their marital difficulties. He persuaded his parents to call a psychotherapist, and eventually their problems were resolved.', "Betsy overheard a heating contractor say that regularly changing the filter in a furnace helps to keep the furnace efficient. So Betsy has regularly changed the furnace filter in her daughter's house. As a result, the furnace has never required maintenance due to becoming clogged with dust or dirt.", 'Sejal learned in a psychology class that the best way to help someone overcome an addiction is to confront that person. So she confronted her friend Bob, who was struggling with a chemical dependency.', "A country's leaders realized that fostering diplomatic ties with antagonistic nations reduces the chances of war with those nations. Because those leaders worried that war would harm their chances of being reelected, they engaged in diplomatic discussions with a hostile country, and the two countries avoided a confrontation."]