Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:The tool differs primarily from the original CHLT-30 in that a Bdon‚Äôt know^ (DK) response option was included for each item because in pilot testing of the instrument, respondents did not feel comfortable guessing and preferred to indicate they did not know [25].
Category: