Final answer:
The Battle of the Coral Sea, conducted in May 1942, was the pivotal encounter that secured Australia from Japanese forces.
Step-by-step explanation:
The WW2 battle that secured Australia from Japanese forces was the Battle of the Coral Sea. This significant engagement between American and Japanese naval forces took place in May of 1942. During this battle, the U.S. Navy successfully thwarted the Japanese invasion aimed at Australia, preventing further advancement towards the Australian mainland. The fight involved no direct contact between surface ships, instead being conducted through carrier-launched aircraft. Although the Battle of Midway in June 1942 was a major turning point in the Pacific War, it was the Battle of the Coral Sea that directly protected Australia from Japanese incursion. Hence, the correct answer to the question would be option C. Battle of Coral Sea.