Correct Option (A)
The passage explicitly states that a diet revolving around "meat and dairy... will take a greater toll on the world's resources - than one that revolves around unrefined grains, nuts, fruits and vegetables." It further notes that this meat and dairy-centric way of eating is on the rise, particularly in the developing world, which exacerbates the resource burden. Therefore, the critical message is the direct relationship between increasing demand for animal-sourced foods and the consequent strain on natural resources.
Incorrect Options:
Option (B): The passage primarily discusses the environmental and resource implications of different diets, not their suitability for human health in developing countries. While plant-based diets may offer health benefits, this is not the central theme conveyed.
Option (C): The passage focuses on the future ramifications of current dietary trends, particularly the rise of meat and dairy consumption in the developing world. It does not discuss the general historical variability of human food habits or their independence from health concerns.
Option (D): The passage does not express uncertainty about which diet is best. Instead, it clearly distinguishes between diets that impose a greater toll on resources (meat and dairy) and those that are less resource-intensive (plant-based), thereby implicitly advocating for the latter from a sustainability perspective.