一伙绑匪把某富翁的爱子绑架,并向其索要5万美元。尽管警方预先在绑匪取赎金的地方设下埋伏,但由于罪犯手段高明,设计把赎金取走了。于是,案情侦破处于停滞状态。两年半后,一名匪徒拿着赎金中的一张钞票去加油站加油时,被警方逮捕。那么警方是在钞票上作了何种标志,没被匪徒发 A group of kidnappers kidnapped the son of a rich man and asked for 50,000 U.S. dollars. Although the police set an ambush in advance where the kidnappers took the ransom, the ransom was taken away because of the cleverness of criminals. So, the case detection is at a standstill. Two and a half years later, a gangster was arrested by a policeman while holding a bill in a ransom to the gas station. So what the police did on the banknote signs, did not be gangsters