The world's longest 3D printed concrete bridge was opened in which of the following countries?

Introduction / Context:
Three-dimensional (3D) printing has moved beyond small objects to large-scale structures like buildings and bridges. This question focuses on an important milestone: the world's longest 3D printed concrete bridge. Knowing where such innovative infrastructure was built helps track global leadership in advanced construction technologies.

Given Data / Assumptions:

• The question asks for the country where the world's longest 3D printed concrete bridge was opened.
• Options are China, Japan, Dubai (United Arab Emirates) and India.
• We focus on a widely reported pedestrian bridge created using 3D printing techniques.

Concept / Approach:
China has invested heavily in 3D printing technology and has been at the forefront of building large 3D printed structures. News reports describe a long 3D printed concrete pedestrian bridge in Shanghai as the world's longest of its kind at the time of its inauguration. While Dubai and other locations also experiment with 3D printed buildings, this specific record for a concrete bridge is associated with China.

Step-by-Step Solution:
Step 1: Recall that the first and longest 3D printed concrete bridge reported internationally was built in Shanghai, China. Step 2: Note that Japan and India are active in technology but do not feature in news as hosting this particular record-holding bridge. Step 3: Dubai is known for futuristic architecture, including some 3D printed offices and structures, but not for the world's longest 3D printed concrete bridge. Step 4: Therefore, among the options, China is the correct country.

Verification / Alternative check:
International engineering and news reports describe a large 3D printed concrete pedestrian bridge in Shanghai that was publicised as the world's longest 3D printed concrete bridge when it opened. Reports about Dubai highlight 3D printed buildings rather than bridges. There is no equivalent widely recognised record in Japan or India. This cross-check supports choosing China as the correct answer.

Why Other Options Are Wrong:
Japan: While technologically advanced, it is not cited as the location of the longest 3D printed concrete bridge.

Dubai (United Arab Emirates): Famous for 3D printed offices and innovative skyscrapers, but not specifically for this record-holding bridge.
India: Actively exploring new technologies, yet not widely reported as having the world's longest 3D printed concrete bridge.

Common Pitfalls:
Students might guess Dubai due to its futuristic reputation or think of Japan or India because of their technological strengths. However, without checking specific news about 3D printed bridges, such guesses can be wrong. This question demonstrates the importance of linking records to particular projects, not just to a general image of a high-tech country.

Final Answer:
Thus, the world's longest 3D printed concrete bridge was opened in China.