Detective: Laser-printer drums are easily damaged, and any nick in a drum will produce a blemish of similar dimensions on each page produced by that printer. So in matching a blemish on a page with a nick on a drum, we can reliably trace a suspicious laser-printed document to the precise printer on which it was produced. Which one of the following, if true, most weakens the detective's argument? ['Most suspicious documents are not produced on laser printers.', 'Criminals are unlikely to use their own laser printers to produce suspicious documents.', 'Drum nicks are usually so small that it requires skill to accurately determine their size and shape.', 'The manufacturing process often produces the same nick on several drums.']