The correct direct object pronoun to fill in the blank is 'vous'. Using direct and indirect object pronouns accurately is important in French grammar.
Je vous téléphone.
In this sentence, the correct direct object pronoun to fill in the blank is vous which represents 'you' in French. The objective case for 'you' as a direct object is 'vous' in French grammar.
Using direct and indirect object pronouns correctly is crucial in constructing sentences in French to convey the intended meaning accurately.