Answer: C) the firm's orientation toward and strategy for global markets and marketing.
Explanation:
International firms are firms that has its main headquarters in a particular country while still having offices in other countries.
For a multinational firms, products are being marketed to different countries in different ways while a transnational firm is a firm that deals with the production of goods and services internationally in more than a country.
The key factor that distinguishes one from another is the firm's orientation toward and strategy for global markets and marketing.