单选题
Your cell phone holds secrets about you. Besides the names and (51) that you've programmed into it, traces of your DNA linger (逗留) on the device, according to a new study.
DNA is genetic material that (52) in every cell. Like your fingerprint, your DNA is unique to you (53) you have an identical twin. Scientists today routinely analyze DNA in blood, saliva (唾液), or hair left (54) at the scene of a crime. The results often help detectives identify (55) and their victims. Your cell phone can reveal more about you (56) you might think.
Meghan J. McFadden, a scientist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the (57) . This made her wonder whether traces of DNA lingered on cell phones even when no blood was involved. (58) , she and colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volunteers. They used swabs (药签) to collect (59) traces of the users from two parts of the phone: the outside, where the user holds it, and the (60) , which is placed at the user's ear.
The scientists scrubbed the phones using a solution made mostly (61) alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got their phones (62) for another week. Then the researchers collected the phones and repeated the swabbing of each phone once more.
The scientists discovered DNA that (63) to the phone's speaker on each of the phones. Better samples were collected from the outside of each phone, but those swabs also picked up DNA that belonged to other people who had apparently also handled the phone. (64) , DNA showed up even in swabs that were taken immediately after the phones were scrubbed (擦洗). That suggests that washing won't remove all traces of evidence from a criminal's device. So cell phones can now be added to the (65) of clues that can decide a crime-scene investigation.