Final answer:
The rezoning by the board of township trustees to allow multi-family residences indicates that the zoning regulations have been changed and the rezoning has become law, reflecting option "c".
Step-by-step explanation:
When the board of township trustees rezones an area to allow for multi-family residences, they are enacting a change in the zoning regulations that control the use and development of property within their jurisdiction. Such a change goes through a process including proposal, consideration, and must be approved before it becomes law. The options provided in the question indicate different stages of this process, with option "c" suggesting that the rezoning has become law, allowing for the construction of multi-family dwellings in the area in question.
Zoning regulations are a key aspect within municipal governance as they help shape the future development and use of land. These regulations must be reasonable, bear a substantial relation to the public welfare, and be necessary for the accomplishment of their purpose. Once the rezoning is approved and enacted, property developers must comply with the new classification when planning their projects.