請依下文回答第 31 題至第 35 題      An unmanned aerial vehicle, commonly known as a drone, is an aircraft without a human pilotaboard. About 700,000 drones were sold in 2015, and the number skyrocketed to almost 3 million in 2017in the U.S. Ordinary people and small businesses use these flying devices to do all sorts of things, fromaerial photography to crop-dusting to just having fun. It also enables shipping to remote places and assistssearch and rescue missions for humans and livestock alike. But the technology has a dark side.     Terrorists and criminals could use drones to conduct illegal surveillance, carry out chemical,biological, and radiological attacks as well as more traditional attacks on large open-air venues such asconcerts, sporting events and government facilities. It was reported that criminals used small drones toblock FBI agents from observing a hostage situation in 2017.     Drones could be used to smuggle as well. Last year, the U.S. Border Patrol agents arrested a 25-yearold man for using a drone to ferry drugs across the southwest border. Since October 2017, officials havereported over three-dozen sightings of drones operating near the U.S. border. The U.S. Customs andBorder Protection is concerned that drones could show smugglers in Mexico vulnerable points on theborder where people and/or drugs can cross over and sneak into the country undetected.     A wide variety of counter-drone measures have been developed in response to this security threat.For example, DJI, the world’s leading maker of unmanned aerial vehicles, enforced geofencing, a virtualgeographical boundary across most of Iraq and Syria, and stopped terrorists from using its drones in bothcountries in 2017. Both France and the Netherlands have been quietly training eagles to take down dronesdeemed as hostile. The Police of Wuhan, China have developed a signal-jamming gun of their own. Thisgun disrupts the drone’s radio signals and forces it to land. Instead of relying on radio frequencies, SkyWalloffers net-based options for polices and governments. It fires projectiles that could be turned into a net to“nonviolently” down the drone.
【題組】31 How can drones benefit us?
(A) They make smuggling easy.
(B) They keep criminals busy.
(C) They make large open events possible.
(D) They save lives after a disaster.