Rewrite the following expression by factoring it completely:
27d³ + 343

• A. (9d + 7)(3d² - 21d + 49)
• B. (7d + 3)(9d² + 21d + 49)
• C. (7d + 9)(3d² + 21d + 49)
• D. (3d + 7)(9d² - 21d + 49)

Answer: (D)