Final answer:
The building that represents the nucleus in the cell city model is the city hall because it is the control center of the city, just like the nucleus is the control center of a cell.
Step-by-step explanation:
The building that should represent the nucleus in the cell city model is the city hall. Just like the nucleus in a cell, city hall is the control center of the city, where important decisions are made and instructions are given. In a cell, the nucleus contains the genetic material (DNA), which serves as the instructions for building proteins and carrying out other important functions.