Answer: The phrase that gives the reader a clue that life in the city is now being discussed is "On the other hand".
Step-by-step explanation: "On the other hand" is a phrase widely used to present an opposed point, opinion or situation. In other words, "on the other hand" is generally used when two sides of an issue are being discussed. In the passage provided, two opposite situations are being discussed: life in the farm and life in the city. The author starts talking about how is living in a farm; however, from sentence 14 onwards, he/she starts talking about how is living in the city . The phrase that the author uses to indicate he/she will be dealing with the opposed situation, that is to say life in the city, is "on the other hand". Therefore, "on the other hand" is the phrase that functions as a clue.