Replace the underlined words with the appropriate interrogative pronoun.De quels livres a-t-il besoin?

“Livres” is masculine plural, so the pronoun replacing “quels livres” is “lesquels.” Because the verb phrase is “avoir besoin de,” the preposition “de” must remain: “de + lesquels” contracts to “desquels.” The correct sentence is “Desquels a-t-il besoin?”

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