Indicate whether each of the following statements is true or false.

a$)$ Plant assets are classified as long$-$term assets, while intangible assets are treated as current assets.

b$)$ Intangible assets include patents, copyrights, and natural resources.

c$)$ Intangible assets with indefinite useful lives will be not be amortized.

d$)$ The cost of land should be depreciated over its useful life.

e$)$ The process of expensing natural resources is called depletion.