Whoever murdered Jansen was undoubtedly in Jansen' s office on the day of the murder, and both Samantha and Herbert were in Jansen' s office on that day. If Herbert had committed the murder, the police would have found either his fingerprints or his footprints at the scene of the crime. But if Samantha was the murderer, she would have avoided leaving behind footprints or fingerprints. The police found fingerprints but no footprints at the scene of the crime. Since the fingerprints were not Herbert' s, he is not the murderer. Thus Samantha must be the killer. Which one of the following, if assumed, allows the conclusion that Samantha was the killer to be properly inferred? ["The fingerprints found at the scene of the crime were not Samantha's.", "The fingerprints found at the scene of the crime were not Jansen's.", "No one but Herbert and Samantha was in Jansen's office on the day of the murder.", 'If there had been footprints at the scene of the crime, the police would have found them.']