Which of these is an example of a two-dimensional presentation aid?

A graph of population growth is a prime example of a two-dimensional presentation aid because it represents data visually on a flat surface using axes to illustrate relationships among different sets of information. In this case, time can be plotted on one axis while population numbers appear on the other, allowing viewers to easily interpret trends and relationships at a glance.

Two-dimensional presentation aids are designed to convey information without the need for three-dimensionality, which is seen in options like a model of a building, a physical representation that occupies space and includes depth. Photos, while visually impactful, are also inherently two-dimensional but do not provide the analytical depth and clarity of data representation as a graph. Similarly, a video presentation, being a sequence of moving images, adds time as a dimension and integrates aspects beyond static two-dimensional visuals. Therefore, the graph stands out as the most appropriate example of a two-dimensional aid in the context of presenting data effectively.