Final answer:
The category of long-lived assets that are depleted over time is c. Natural resources, which are a form of tangible assets.
Step-by-step explanation:
The category of long-lived assets that are depleted over time is c. Natural resources. These are considered a subset of tangible assets, which include physical items such as land, minerals, oil reserves, and timber. Unlike other long-lasting durable goods like cars and refrigerators, or collectibles like paintings or jewelry, natural resources are inherently consumed and thus depleted through their use. Unlike current assets, such as inventories that are meant to be sold within a year, natural resources are intended for use over a longer period but will diminish as they are extracted and utilized.