Final answer:
To add an adjective and a noun complement to the given sentences.
Step-by-step explanation:
To add an adjective and a noun complement to the sentence a. Tu montes un cheval, you can say Tu montes un grand cheval noir.
To sentence b. A-t-elle retrouvé la clé?, you can add an adjective and a noun complement by saying A-t-elle retrouvé la petite clé en argent?
To sentence c. Nous lui offrirons des chocolats, you can add an adjective and a noun complement by saying Nous lui offrirons des délicieux chocolats belges.
To sentence d. J'ai acheté un livre, you can add an adjective and a noun complement by saying J'ai acheté un livre intéressant sur l'histoire.
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