Which country has built the world's largest amphibious aircraft for both land and water operations?

Introduction / Context:
Defence technology and aviation milestones are frequently asked in competitive exams. One such milestone was the development of the AG600 “Kunlong”, which is described as the world's largest amphibious aircraft, capable of taking off and landing on both land and water. The question tests whether you know which country designed and built this record breaking aircraft.

Given Data / Assumptions:

• The phrase “world's largest amphibious aircraft” refers to a modern, large scale seaplane.
• The options provided are four technologically advanced countries: Japan, Russia, China, and India.
• We assume the question is about the AG600 aircraft that drew global media attention around 2016–2017.

Concept / Approach:
Amphibious aircraft can operate from both conventional runways and water surfaces, making them useful for maritime patrol, search and rescue, and firefighting. The AG600 was developed by the Aviation Industry Corporation of China (AVIC). Remembering that “Kunlong” and “AG600” are linked with China helps you answer this question quickly. Other countries also have amphibious aircraft, but the “world's largest” descriptor is specifically associated with China's AG600.

Step-by-Step Solution:
Step 1: Recall any news you might have read about a giant amphibious aircraft conducting its maiden flight in China. Step 2: Connect the model name AG600 “Kunlong” with the country that produced it, which is China. Step 3: Compare this recollection with the options: Japan, Russia, China, and India. Step 4: Select “China” as it correctly matches the country known for building this particular aircraft.

Verification / Alternative check:
Another way to verify is to recall that the AG600 complements China's broader ambitions in the South China Sea and maritime areas. News articles often highlighted that the aircraft was designed to support island building, sea patrols, and firefighting missions, again tying it clearly to China.

Why Other Options Are Wrong:

• Japan: Japan has manufactured notable amphibious aircraft like the ShinMaywa US-2, but it is not described as the world's largest in this context.
• Russia: Russia has many large aircraft and seaplanes, but the news item about the “world's largest amphibious aircraft” in recent years refers to China's AG600.
• India: India operates various aircraft but has not designed and built the world's largest amphibious aircraft.

Common Pitfalls:
Because Russia and Japan also appear frequently in defence related questions, some students guess one of these countries without recalling the specific model name and headlines. To avoid confusion, always associate “AG600 Kunlong” directly with China in your notes. Linking key defence projects to their originating country is a useful exam strategy.

Final Answer:
The world's largest amphibious aircraft was built by China.