In a classified balance sheet, assets are usually classified as:

a. current assets; long-term assets; property, plant, and equipment; and intangible assets.

b. current assets; long-term investments; property, plant, and equipment; and other assets.

c. current assets; long-term investments; property, plant, and equipment; and intangible assets.

d. current assets; long-term investments; tangible assets; and intangible assets.