**Explanation:**

**Acquisition** is the correct answer.

**Merger** refers to the combination of two or more companies that come together to form a new entity. In a merger, both companies involved contribute their assets and liabilities to create a new company, and the original companies cease to exist as separate entities.

**Strategic alliance** refers to a partnership or collaboration between two or more companies to achieve a specific objective. Strategic alliances are formed to leverage the strengths of each company and to gain a competitive advantage in the market.

On the other hand, **acquisition** refers to the purchase of one company by another, resulting in the acquiring company gaining control over the acquired company. The acquiring company becomes the new owner of the acquired company, and the acquired company may continue to operate as a subsidiary or may be merged into the acquiring company.

Acquisition can occur in several ways:

1. **Asset acquisition**: The acquiring company purchases specific assets of the target company, such as its intellectual property, equipment, or real estate.

2. **Stock acquisition**: The acquiring company purchases a majority or all of the target company's shares, gaining control over the target company.

3. **Mergers and acquisitions (M&A)**: M&A is a term often used to refer to the acquisition of one company by another. In this case, the acquiring company may merge with the target company, combining their operations and resources.

Acquisitions are often pursued by companies to achieve various objectives, such as:

- **Expansion**: Acquiring another company allows the acquiring company to expand its market presence, customer base, product portfolio, or geographic reach.

- **Synergy**: Acquisitions can create synergies by combining the strengths and resources of both companies, leading to increased efficiencies and cost savings.

- **Diversification**: Acquiring a company in a different industry or market segment can help the acquiring company diversify its business and reduce risk.

- **Competitive advantage**: Acquiring a competitor or a complementary business can give the acquiring company a competitive advantage by eliminating competition or gaining access to new technologies or capabilities.

In conclusion, when a company clearly becomes the new owner of another company, the action is called an acquisition.