insoluble

mastery
UK /ɪnˈsɒljʊbəl/ US /ɪnˈsɑljəbəl/adjnoun

card 1 of 10 · definition

Which adverb most naturally collocates with 'insoluble' to mean 'apparently impossible to solve'?

Which adverb most naturally collocates with 'insoluble' to mean 'apparently impossible to solve'?