The value of the term independent of x in the expansion of $$\left(3x - \frac{4}{x^2} \right)^9$$ is

A

$$7 \times 3^7 \times 2^8$$

B

$$7 \times 3^8 \times 2^7$$

C

$$-7 \times 3^7 \times 2^8$$

D

$$-7 \times 3^8 \times 2^7$$