It used to take Redwood City,California police hours to locate g

It used to take Redwood City,California police hours to locate gunfire．Now,they have a new tool that helps them find the gunfire quickly．This new tool is called the Shot Spotter,The police began using the Shot Spotter in 1995．They wanted to cut down on gunfire in their city. One Shot Spotter covers a square mile．Eight microphones are put on the roofs of buildings．These microphones pick up gunfire noise．It only takes seven seconds to report the gunfire to the police．Then a red dot on the police map shows where the action is. The Shot Spotter really works well．It locates the gunfire within 20 to 40 feet plus or minus．Redwood City police are very happy with the Shot Spotter．They think it might have helped catch the D. C．sniper. Shot Spotters cost a lot of money．One of them sells for$200,000．Despite the cost,Shot Spotters can be a big help in fighting crime. Eight microphones placed on rooftops__.
A、talk to police
B、warn the public
C、listen for gunfire
D、play rap music
【正确答案】：C
【题目解析】：文中明确提到“Eight microphones are put on the roofs of buildings. These microphones pick up gunfire noise.”，意思是八个麦克风被放在建筑物屋顶，这些麦克风是用来收集枪击噪音的，也就是用来监听枪击声的，选项 C 正确。选项 A 与原文不符，它们不是和警察交谈；选项 B 文章未提及；选项 D 说播放说唱音乐更是无中生有。所以答案选 C。