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SFI connects "filler" subjects "it" and "there" to invertible verbs in questions with subject-verb inversion:

        |   |
        Is it likely that Jane will go
        Is there going to be a problem
Both the use of "it" and "there" and the use of subject-verb inversion are highly constrained by post-processing (see "SF"; see "SI"). However, there is nothing especially problematic about SFI; SFI is to SF precisely as SI is to S.

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