Here's why:

* Specimen: A specimen is a sample of an organism or a part of an organism that is preserved for scientific study or display. This preservation often involves techniques that prevent decay.

* Other possible words:

* Artifact: This refers to an object made by humans, and while it can be preserved, it doesn't always imply protection from decay.

* Relic: This refers to something of historical or religious significance, and it can be preserved, but it's not the most precise term for a preserved organism.

Therefore, specimen is the most accurate word to describe an actual organism or parts of it that are protected from decay.