Final answer:
The correct completion of the sentence is 'nosotros somos altos'.
Step-by-step explanation:
The correct completion of the sentence is nosotros somos altos. Somos is the appropriate verb form for the subject nosotros, which means 'we' in Spanish. The adjective altos matches the subject nosotros in both gender and number, agreeing in gender and number with the noun it modifies.
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