Final answer:
The 'big 3' of survival are oxygen, water, and nutrients, which are essential components for human survival. They support vital functions, including respiration, digestion, temperature regulation, energy, growth, and repair.
Step-by-step explanation:
The 'big 3' of survival often refer to the most basic and essential resources that humans need to survive: oxygen, water, and nutrients (like carbohydrates, lipids, proteins, vitamins, and minerals). Without oxygen, humans cannot survive more than a few minutes as it is essential for respiration—the intake of oxygen and the release of carbon dioxide. Water is critical as humans can endure only several days without it, and it plays a key role in many bodily functions including digestion and temperature regulation. Lastly, nutrients are necessary for the body's energy, growth, and repair, and we cannot go without them for more than several weeks. These three elements are crucial for maintaining human survival, and any long-term exposure to conditions that deprive individuals of these requirements such as extreme heat, cold, or inappropriate atmospheric pressure is not compatible with survival.