Final answer:
In 'Araby,' the tone shifts due to the protagonist's infatuation with Mangan's Sister, which brings about a sense of romantic longing and marks a transition in the protagonist's journey. So, the correct answer is Option C, the protagonist's infatuation with Mangan's Sister.
Step-by-step explanation:
In James Joyce's short story "Araby," the tone shifts when the protagonist becomes infatuated with Mangan's Sister. This is a pivotal moment that transitions the narrative from the mundane reality of the protagonist's life into a more fervent and quest-like narrative. The protagonist's infatuation with Mangan's Sister brings a new level of intensity and longing to the story as he embarks on a journey to the Araby bazaar with the hope of obtaining something that will impress her.
The youthful innocence and idealization of love are clearly projected against the backdrop of a grey and parochial Dublin. This infatuation is represented as a change from the typical world of the protagonist to a new world of romantic adventure and possibilities. The mention of the correct option in the final part of this tutorial's response is essential. The question asked was about the factor that triggers a shift of tone in "Araby". The correct answer is Option C, the protagonist's infatuation with Mangan's Sister.