Pandora Pandora 01-02-2024 Mathematics High School Simplify this expression: \( 3x^2(7x^2 − 9) \)A. \( 21x^2 − 9 \)B. \( 21x^2 − 27x^2 \)C. \( 21x^4 − 9 \)D. \( 21x^4 − 27x^2 \)