Final answer:
Land generally does not depreciate over time, which makes it the asset from the provided options that does not decline in service potential over its useful life.
Step-by-step explanation:
The student's question pertains to which types of plant and equipment assets do not decline in service potential over time. In accounting, most plant assets like buildings and equipment depreciate, or lose value, as they age and are used. However, the asset mentioned in the options that generally does not depreciate is land. Land typically does not decline in service potential over time while the other assets listed do. Land does not wear out, become obsolete, or get used up the way buildings, equipment, and land improvements can. Therefore, the correct answer is option c) land, which remains an enduring asset with sustained potential utility, barring external factors that might affect its value.