Final answer:
It has been estimated that if everyone in the world had the same lifestyle as the average American, it would require five more Earths. So, the correct answer is option b. five.
Step-by-step explanation:
The question addresses the issue of global resource use in the context of living standards equivalent to those of the average American. When considering energy usage, which is about five times the global average for Americans, extrapolating this rate to the entire global population would result in a massive increase in consumption. Current estimates suggest that to sustain 7 billion people at the American standard of living, we would require the resources equivalent to five more Earths.
This issue highlights the concept of carrying capacity, which refers to the maximum population size of a species that an environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment. With our existing population, we are already placing significant strain on the planet's resources.
Moreover, considering income inequalities and purchasing power disparities, not all countries can currently achieve the lifestyle and consumption rates of industrialized countries without causing severe ecological devastation.
According to the options provided, the correct answer is b. five.