Rule reminder
Advanced Italian sentences often contain multiple subordinate clauses simultaneously: a concessive clause plus a relative clause, temporal clause, causal clause, or conditional. Correctly identifying the function of each subordinate clause and choosing the appropriate mood is essential at B2 level. The concessive clause always requires the subjunctive (with sebbene/benché/nonostante) while other clause types follow their own rules.
In the sentence 'I dati, benché fossero stati raccolti in modo rigoroso e che mostrassero tendenze chiare, non convinsero il comitato', there is a grammatical error. What is it?