Which of the following statements is true regarding direct and indirect costs?

A. Direct costs can be easily traced to a specific cost object, while indirect costs cannot.

B. Indirect costs are always fixed costs, while direct costs are always variable costs.

C. Direct costs are always manufacturing costs, while indirect costs are always period costs.

D. Indirect costs are always allocated to products, while direct costs are always expensed as period costs.

E. None of the above.