What defines the aim to retain materials from significant historical periods while removing others?

The correct choice centers around the concept of restoration, which specifically involves returning a property to its former state from a particular historical period while retaining its significant materials and removing later alterations that are not representative of that period. Restoration aims to accurately depict the character of a historic property as it appeared during a specific time frame while ensuring that the original materials are preserved and honored in the process.

This approach distinguishes itself from other options, such as preservation, which focuses on maintaining the current state of a property without making significant alterations or removing materials, regardless of their historical significance. Rehabilitation, on the other hand, involves making a property usable for its intended purpose while retaining significant historical features, but it allows for more alterations than restoration does. Reconstruction is a more drastic approach that entails re-creating lost or damaged features of a property based on historical evidence, rather than preserving existing significant materials.

In summary, restoration is defined by its aim to return a property to a specific historical period, emphasizing the retention and respect of original materials while excluding non-historic elements, thereby making it the most accurate choice in this context.