Which of these agricultural practices is sustainable? a. using less water to grow crops that are less water dependent b. using factory farming to increase the food supply c. using groundwater to irrigate crops d. using water from another region to irrigate crops

B is unsustainable as this is a practice of intensive farming usually conducted indoors, and is resource and energy expensive. C is unsustainable because groundwater is a limited resource and groundwater can take 1000s of years to be recharged. D is unsustainable as this involves moving water across vast distances and is expensive and ecologically damaging. A is sustainable as drought-resistant plants would in the long run use less water.