nayana-c1.867c992ae9100904cc61c84591adf0f8f863e0387e30f0d0dbc86640e9f50a1a.en.test.15148

The task

Which sources of non-confluence in the standard sequent calculus are avoided in proof forests? A. a cut on two weakenings and a cut on two contractions B. a cut on two existential formulae and a cut on two universal formulae C. a cut on two propositional cuts and a cut on two first-order proofs D. a cut on two polarised forests and a cut on two non-polarised forests Return only the single uppercase letter of the correct option.