The tone of the story changes through it's development, being described while we are given the description on the environment around the Boy, Tito.
At first, we have a joyful tone, when the narrator describes an lively, active city and a beautiful friendship between the dog and the blind homeless boy, Tito.
We feel how important one friend is for the other and see that although their life is not easy, they will always have each other to count on.
When the two friends arrive at the forum, as we get to know the story of the earthquake and the characters hear the dialogue between Rufus and the foreign, that states that the Volcano column of smoke are at an unusual height, the tone of the story changes, giving us and uneasy feeling and preparing us for what would come later.
Later on, the thrilling of the running friends starts to bring fear and desperation inside the reader and lastly, sadness , as we know the dog has died in order to save his friend.
So the right answer would be A, as the tone depends on the description of the facts that are happening with the main characters, that create a specific mood given by the author, though the adjectives used.
