Final answer:
A synergistic strategic alliance aligns closely with a business-level horizontal complementary alliance, which involves companies at the same production stage sharing risks and responsibilities to focus on their core competencies.
Step-by-step explanation:
The synergistic strategic alliance, which is similar to the business-level horizontal complementary alliance, creates synergy across multiple functions or multiple businesses between partner firms. This type of alliance brings together firms that are at the same stage of production or in the same industry but do not necessarily compete directly. Firms involved in such an alliance share responsibility and risk and benefit from each other's complementary skills to assist in the management of their businesses, often focusing on enhancing their core competencies.
A vertical merger, in contrast, involves companies joining together from different steps of manufacturing to protect against the loss of suppliers and to streamline the manufacturing process. Therefore, among the options provided, the most similar to a synergistic strategic alliance is a horizontal complementary alliance, which allows companies at the same stage of the supply chain to make all business decisions collaboratively, leveraging shared strengths for mutual benefits.