The correct answer is: b) Remote rural areas.
Mobile veterinary units are vehicles that are equipped with veterinary supplies and equipment. They travel to remote rural areas to provide essential healthcare services to livestock. These services include vaccinations, deworming, and treatment of injuries and illnesses. Mobile veterinary units play an important role in improving the health and welfare of livestock in remote areas.
Option a) is incorrect because urban areas are typically well-served by veterinary clinics. Option c) is incorrect because flood-prone regions are not necessarily remote rural areas. Option d) is incorrect because livestock markets are not typically equipped to provide veterinary care.