What Is the Definition of Depreciation

What is the definition of depreciation?

A) Depreciation is a special type of prepaid item involving fixed assets and it is the allocation of an asset's cost over its useful life.
B) Depreciation is a special type of accrued liability item involving fixed assets and it is the allocation of an asset's cost over its useful life.
C) Depreciation is a special type of prepaid item involving revenues and it is the allocation of an asset's cost compared to revenue generated over its useful life.
D) Depreciation is a special type of prepaid item involving a current prepaid asset and it is the allocation of the prepaid's cost over the asset's life.