Which one of the following statements is correct?

Select one:

a.

Natural resource assets are typically depleted using the straight-line method

b.

The research costs of a new drug can be capitalized on the balance sheet as an intangible asset

c.

All intangible assets are amortized over their useful lives

d.

Trademarks and patents are classified as property, plant and equipment

e.

The depletion expense for natural resources extracted is added to inventory