Final answer:
The sentence 'Maria est amérindien' is grammatically incorrect. The correct form should be 'Maria est amérindienne'.
Step-by-step explanation:
The sentence 'Maria est amérindien' is grammatically incorrect. The word 'amérindien' is a masculine noun, so the correct form should be 'Maria est amérindienne' with an extra 'e' at the end of the adjective to agree with the feminine subject 'Maria'.
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