The International Court of Justice (ICJ), the principal judicial organ of the United Nations, consists of 15 judges. These judges are elected by the UN General Assembly and Security Council for nine-year terms. They represent different legal systems of the world and ensure fair representation. The ICJ settles disputes between states and gives advisory opinions on legal questions. Thus, 15 is the correct answer, reflecting the structure of this global judicial body.

The Paris Climate Conference, officially known as COP21, was held in 2015 in Paris, France. It brought together representatives from nearly every country to address the growing threat of climate change. The conference resulted in the historic Paris Agreement, a global pact aimed at limiting the rise in average global temperatures to well below 2°C above pre-industrial levels, with efforts to restrict it to 1.5°C. This agreement is significant because it marked the first time that both developed and developing nations committed to reducing greenhouse gas emissions. Countries pledged to set nationally determined contributions (NDCs), which outline their climate action plans. The agreement also includes mechanisms for monitoring progress and providing financial support to developing nations. The other options are incorrect because the Paris Agreement was specifically finalized in 2015. The year 2016 is associated with the agreement entering into force, not its negotiation. Understanding the timeline of global environmental agreements is important in competitive exams and helps in building awareness of international cooperation. Therefore, 2015 is the correct answer as it represents a milestone in climate diplomacy and global environmental governance.

Producers, mainly green plants, require nitrogen for synthesizing proteins, nucleic acids, and chlorophyll. However, they cannot directly use atmospheric nitrogen (N₂), which is chemically inert. Instead, they absorb nitrogen in usable forms such as ammonia (NH₃), ammonium ions (NH₄⁺), or nitrates (NO₃⁻). Ammonia is produced through biological nitrogen fixation by certain bacteria, which convert atmospheric nitrogen into a form plants can absorb. This process is crucial for maintaining the nitrogen cycle in ecosystems. CO₂ is used by plants in photosynthesis but does not provide nitrogen. N₂, although abundant in the atmosphere, cannot be directly utilized by plants without conversion. NH₄NO₃ is a fertilizer that provides nitrogen, but the fundamental absorbed form at the biochemical level is ammonia/ammonium. Thus, NH₃ is the correct answer. Understanding nutrient cycles is essential for grasping ecosystem functioning and is a common topic in competitive exams. This concept highlights the importance of microorganisms in supporting plant life and maintaining ecological balance.

Max Planck, a German physicist, is known as the father of quantum theory. In 1900, he proposed that energy is emitted in discrete packets called quanta, rather than continuously. This idea explained blackbody radiation, which classical physics could not. Quantum theory revolutionized physics and led to the development of quantum mechanics. It explains the behavior of particles at atomic and subatomic levels and forms the basis of modern technologies like semiconductors and lasers. Gravitational theory is associated with Isaac Newton, while the theory of relativity was developed by Albert Einstein. “Quality theory” is not a scientific concept. Thus, the correct answer is quantum theory. Planck’s work marked the beginning of modern physics.

The Rio Earth Summit was held in June 1992 in Brazil and focused on sustainable development and environmental protection.