Answer:
B. knowledge capital is both nonrival and nonexcludable; other firms can freely access the research and development of one particular firm.
Step-by-step explanation:
Knowledge and capital are non-exclusive, firms may in the long run have access to research and development by other firms. In the short term, companies may be protected by patents. However, in the long run, patents expire and scientific knowledge becomes a common good, so everyone can have access. This acts as a disincentive for firms to invest in research and development. For economic growth the effect is very bad, since if all firms invested in knowledge, productivity would tend to increase significantly, increasing the GDP and wealth of nations.