Final answer:
The firm's core competency is its research and development.
Step-by-step explanation:
In this example, the firm's core competency would likely be its research and development (option A). The fact that the company has just announced the discovery of a revolutionary new drug for dieting suggests that its research team has developed a product that sets it apart from competitors. While the other options (human resources abilities, financing activities, and operating activities) are important functions within a business, they do not directly relate to the firm's ability to develop innovative products like the new drug for dieting.