The terms "open" and "closed" have two related meanings in regard to pronunciation: open vowels and closed vowels, and open syllables and closed syllables.
The second form of the conditional perfect is the literary equivalent of the conditional perfect.
Indefinite relative pronouns (ce dont, ce que, ce qui, ce à quoi) are connectors: they link relative clauses to main clauses and, unlike normal relative pronouns, do not not have a specific antecedent.
Verbs of perception are subject to grammatical agreement in the compound tenses, but the rules are somewhat tricky - they only agree with their subjects when they precede the verb.
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