Multiply the polynomials.

$\left(x+4\right)\left(3x^2-2x+1\right)$

• A. $3x^3+10x^2-7x+4$
• B. $3x^3+12x^2+x+4$
• C. $12x^2-8x+4$
• D. $3x^3-2x^2+x$