Answer the following question: Read the article and select the best answer. Article: Your cell phone holds secrets about you. Besides the names and numbers that you've programmed into it, traces of your DNA remain on it, according to a new study. DNA is genetic material that appears in every cell. Like your fingerprint, your DNA is unique to you --- unless you have an identical twin. Scientists today usually analyze DNA in blood,saliva , or hair left behind at the scene of a crime. The results often help detectives identify criminals and their victims. Meghan J. McFadden, a biologist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the device. This made her wonder whether traces of DNA remained on cell phones --- even when no blood was involved. To find out, she and a colleague collectedflip-style phones from 10 volunteers. They collected invisible traces of the users from two parts of the phone: the outside, where the user holds it, and the speaker, which is placed at the user's ear. The scientists scrubbed(meaning "cleaned") the phones using a liquid mixture made mostly of alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got their phones back for another week. Then the researchers collected the phones and repeated collecting traces on each phone once more. They discovered DNA that belonged to the phone's owner on each of the phones. Surprisingly, DNA showed up even in swabs that were taken immediately after the phones were cleaned. That suggests that washing won't remove all traces of evidence from a criminal's cell phone. So cell phones can now be added to the list of clues that can help a crime-scene investigation. Question: The scientists allowed the volunteers to keep their cell phones for a week in order to _ . Options: A: let them leave their traces on their phones B: avoid keeping their cell phones too long C: give them a chance to get rid of their secrets D: find out who is responsible for the crime
Answer:
A