Option (a) is incorrect because it suggests reversing the emerging trend of food consumption, which is impractical. Also, the passage does not solely deal with dietary trends. It also talks about trends in transportation and gadget use.

Option (b) is incorrect. The statement seems logical but is not the crux of the passage because it suggests improving agricultural and energy efficiency separately without dealing with the core issue of water use efficiency that is common to both agriculture and energy production.

Option (c) is incorrect. According to the passage, the changing trends in consumption behavior are due to the growing affluence among the middle class, and not solely due to modern technological developments. It is affluence that enables access to modern technological developments like gadgets and vehicles.

Option (d) is the correct answer. The passage clearly mentions that switching from cereal-based to protein-based diets entails increased water consumption. Increasing use of machines and vehicles also requires more energy, which in turn needs water to generate. Both changing dietary practices and energy use practices put a strain on water resources. As the number of middle-class families with water-intensive habits is set to rise exponentially, water management practices will also need to change dramatically in the coming years.