Rule reminder
After superlative relative clauses (il più... che, il meno... che) and after restrictive expressions (l'unico che, il solo che, il primo che, l'ultimo che), the subjunctive is used. These constructions imply a judgment or evaluation where the speaker's perspective frames the statement as opinion rather than objective fact.
This is the most interesting article I have ever read. Choose the correct form: 'È l'articolo più interessante che _____ mai letto.'