The correct answer is option 'A': Italy, Germany, Japan.

The Tripartite Pact, also known as the Axis Pact, was signed on September 27, 1940, and it established the Axis Powers during World War II. This alliance was formed between three major countries: Italy, Germany, and Japan. Let's take a closer look at each of these countries and their reasons for signing the pact.

Italy:
- Italy, under the leadership of Benito Mussolini, had already formed an alliance with Nazi Germany through the Pact of Steel in 1939. This pact aimed to strengthen their military cooperation and shared ideologies.
- Mussolini saw the Tripartite Pact as an opportunity to solidify Italy's position within the Axis Powers and gain support for his expansionist policies in Europe and Africa.
- By joining forces with Germany and Japan, Italy hoped to expand its colonial empire and regain its former glory as a major world power.

Germany:
- Nazi Germany, led by Adolf Hitler, sought to establish a new world order based on fascist ideology and territorial expansion.
- Hitler saw the Tripartite Pact as a means to secure his eastern front and gain access to vital resources in Asia.
- By aligning with Italy and Japan, Germany aimed to strengthen its military and economic capabilities, as well as gain political support for its aggressive actions in Europe.

Japan:
- Japan, under Emperor Hirohito, was pursuing its own imperialistic ambitions in East Asia.
- The signing of the Tripartite Pact allowed Japan to secure a powerful alliance with Germany and Italy, which provided military support and access to resources.
- Japan's main goal was to establish dominance in the Pacific region and create a Greater East Asia Co-Prosperity Sphere, which aimed to exploit the resources of Southeast Asia and establish Japanese hegemony.

In conclusion, the Tripartite Pact was signed by Italy, Germany, and Japan. Each of these countries had their own motives for joining the pact, but ultimately they sought to strengthen their military capabilities, expand their territories, and promote their shared fascist ideologies.