Which of the following statements is true?

I. When a company is involved in more than one activity in the entire value chain, it is vertically integrated.

II. A vertically integrated company is less dependent on its suppliers than a company that is not vertically integrated.

III. A disadvantage of vertical integration is that by pooling demand for parts from a number of companies, a supplier may be able to enjoy economies of scale that result in higher quality and lower cost than if every company makes its own parts.

a. Only statement III is true.

b. None of the statements are true.

c. All of the statements are true.

d. Only statement I is true.