Final answer:
Large Animal Mobile Units/Fully Equipped Trucks are used as emergency response vehicles to provide onsite veterinary care to large animals in urgent situations.
Step-by-step explanation:
Large Animal Mobile Units or Fully Equipped Trucks are typically used as emergency response vehicles. These specialized vehicles are designed to provide veterinary care in various situations, especially when rapid medical response is needed in the field. They are equipped with medical supplies and equipment necessary for treating large animals, such as horses and cattle, and are essential for veterinarians who need to conduct medical procedures onsite at farms, stables, or rural areas.
The mobile units are extensively used in situations where transportation of the animal to a stationary veterinary clinic is impractical or impossible due to the animal's size, condition, or the urgency of the medical care needed. Therefore, the correct answer is (d) Emergency response vehicle.