Step 1: Understanding the Question: The core objective here is to correctly identify the primary target category of gases that the Kyoto Protocol was internationally drafted to reduce.
Step 2: Key Concept: The Kyoto Protocol is a landmark international treaty that operationalized the United Nations Framework Convention on Climate Change (UNFCCC).
Step 3: Detailed Explanation:
Formally adopted in \(1997\) in Kyoto, Japan, the protocol boldly commits industrialized nations and economies in transition to strictly limit and systematically reduce their emissions of greenhouse gases (GHGs).
The protocol meticulously targets a recognized basket of six major GHGs responsible for global warming: Carbon dioxide (\(CO_2\)), Methane (\(CH_4\)), Nitrous oxide (\(N_2O\)), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulfur hexafluoride (\(SF_6\)).
Evaluating the other options: Ozone-depleting gases are robustly handled by the Montreal Protocol, not Kyoto.
Noble gases are chemically inert and have absolutely no bearing on climate change dynamics.
Radioactive gases are governed by separate nuclear safety treaties and are completely unrelated to the Kyoto Protocol's mandate.
Step 4: Final Answer: The Kyoto Protocol was primarily designed to reduce greenhouse gases.