Rule reminder
Substitution replaces a word or phrase with a pro-form to avoid repetition. In Italian: (1) PRO-VERBAL substitution: 'farlo/farne/farcela' replace a verb phrase. (2) NOMINAL substitution: 'quello/quella + relative clause' replaces a noun phrase. (3) TALE: formal substitute for a noun just mentioned. These devices create cohesion while avoiding tedious repetition.
«Dovevo studiare, ma non ho voluto ___.» Cosa sostituisce 'farlo' qui?