Which of the following marketing strategies is not based on the notion of network externalities in high-tech markets?

a. Firms may give products away for free in order to seed the adoption of its product by a large number of customers.
b. Firms may partner with competitors in order to establish an industry standard, so that competing products will work with each other.
c. Firms may decide to keep the basis of its technology proprietary, so that competitors and complementors cannot undermine the basis of its competitive advantage.
d. Firms will want to license its technology to competitors and sell its components to OEMs in order to enlarge the size of the installed base.
e. All of the above are consistent with the notion of network externalities.

c