IV. Reading Comprehension:
 Passage A
      Does the word “drone” conjure up thoughts of sci-fi flicks or images of attacks carried out remotely onhostile lands? You may be surprised to learn that drones are acquiring many non-military uses these days.One drone manufacturer, Arad Metering Technologies, is using these remote-controlled flying machines inIsrael to help save water. The company’s battery-operated drones are among the novel tools deployed byArad to help consumers and companies conserve H2O and make money, too.
      That such an idea would come out of Israel is no coincidence. The country is poor in water and rich intech innovation. Israel pioneered the use of unmanned aerial vehicles after it lost many fighter jets in the1973 war. But Arad’s drones don’t fight. They read data from the company’s patented water-meter system todetect leakage in irrigation systems to prevent drought.
      Thousands of miles away, drones are being enlisted in the fight against crime. In several U.K. cities,police agencies are employing drones in place of far more expensive manned helicopters. Though the dronesare not very large, they are capable of carrying cameras and devices that detect body heat. A policeman canoperate one of these drones using a remote control. By wearing special glasses, he or she can see exactlywhat the drone sees as it flies. In one incident, a policeman used a drone to follow a suspected car thief. Evenafter the suspect disappeared in thick fog, the officer was able to track him with the drone and guide fellowpolicemen to his location. Police agencies have found more uses for drones, such as border protection andmaritime security.
31. What does this article describe?
(A) Audio equipment.
(B) Robots for factories.
(C) Popular hiking gear.
(D) Small-scale aircraft.