Final answer:
The correct answer is d. unrelated diversification; related diversification. Companies may have diversified into new industries to adapt to changing market conditions and take advantage of new opportunities.
Step-by-step explanation:
The correct answer is d. unrelated diversification; related diversification.
In the question, it is stated that research suggests that unrelated diversification has increased while related diversification has decreased. This suggests that companies have been expanding into new, unrelated markets while reducing their presence in related markets.
This may be due to the restructuring that took place in the 1990s and early twenty-first century. Companies may have diversified into new industries to adapt to changing market conditions and take advantage of new opportunities.