Researchers trying to make it possible to trace counterfeit documents to the printer that produced them are (i) ________ the fact that the rotating drums and mirrors inside laser printers are imperfect devices that leave unique patterns of banding in their output. Although these patterns are (ii) __________ to the naked eye, they can be (iii) _________ and analyzed by computer programs that the researchers have spent the past year devising.
the first blank - from the sentence we can deduce that the blank should be something like “using”, but is there any particular strategy from the toolkit that can be used here? I am just trying to solve all the blanks with particular strategy so that I don’t use my ear