A properly built pond should limit its depth to discourage what?

The correct choice is focused on limiting aquatic vegetation growth. A properly constructed pond is typically designed with a shallower depth in certain areas to discourage the excessive growth of aquatic plants and algae. Shallow waters provide optimal conditions for sunlight penetration and nutrient availability, which can lead to overgrowth if depth is not managed. By limiting the depth, the growth of unwanted aquatic vegetation can be controlled, thereby maintaining a healthier balance in the pond's ecosystem.

While fish populations, water evaporation, and bacterial growth can also be influenced by pond depth, they are not the primary concern when designing a pond to manage vegetation. The goal is often to create a balance that supports a diverse aquatic ecosystem while preventing issues related to overgrowth, which can obstruct water flow and degrade water quality. Thus, managing depth effectively serves as a critical factor in vegetation control.