D) By providing a different perspective and encouraging the Englishman to never give up, the boy helps him to discover the alchemist.
When the Englishman and Santiago first meet, they understand that they are both trying to follow their Personal Legends. On their travels through the desert, they recognize that each has a different way of trying to accomplish their goal. The Englishman turns to books and research for his answers, while the boy observes the world around him. They each try the other's way of doing things, but the Englishman gives up quickly. However, at the oasis, the boy reminds the Englishman that the people of the oasis might call the alchemist something else, and this insight helps the Englishman.