The correct answer is Option 2: European Organization for Nuclear Research (CERN).

In the year 2008, the European Organization for Nuclear Research (CERN) conducted a complex scientific experiment in which sub-atomic particles were accelerated to nearly the speed of light. This experiment was carried out at the Large Hadron Collider (LHC), which is located near Geneva, Switzerland.

The Large Hadron Collider is the world`s largest and most powerful particle accelerator. It consists of a 27-kilometer underground ring, where particles are accelerated to extremely high speeds and made to collide with each other. These collisions generate an enormous amount of energy, allowing scientists to study the fundamental properties of matter and the universe.

CERN`s experiments at the LHC aim to explore various aspects of particle physics, including the search for the Higgs boson, which was successfully discovered in 2012. Accelerating sub-atomic particles to nearly the speed of light allows scientists to recreate the conditions that existed shortly after the Big Bang, providing insights into the fundamental building blocks of matter and the early universe.

CERN`s research has significant implications for our understanding of the universe and has led to groundbreaking discoveries in the field of particle physics. The experiments conducted at the LHC involve a vast international collaboration of scientists from different countries and institutions, making it a truly global scientific endeavor.

In contrast, the other options listed do not pertain to particle physics or experiments involving sub-atomic particles. The European Space Agency (ESA) primarily focuses on space exploration, satellite deployment, and other related activities. The International Atomic Energy Agency (IAEA) is responsible for promoting the peaceful use of nuclear energy and ensuring nuclear safety and security. The National Aeronautics and Space Administration (NASA) is the United States` space agency, involved in space exploration and aeronautics research.

Therefore, based on the information provided, the European Organization for Nuclear Research (CERN) is the organization that conducted the complex scientific experiment involving sub-atomic particles accelerated to nearly the speed of light in the year 2008.