Answer:
D. strategic alliance
Explanation:
A strategic alliance is a partnership between two companies in which they get an opportunity to achieve goals that can't be reached without both parties, but they stay as independent businesses. Also, this alliance should resul in an increase in the revenue and the market share for both companies. Considering that in this case, Casca Paint Inc. and Designs Inc. made an agreement to offer customers a complete interior design solution that can provide benefits for both companies, this is an example of a strategic alliance.