Tìm nguyên hàm
$\int{{{{{(2+{{e}^{{3x}}})}}^{2}}dx}}.$
A. $4x+4{{e}^{x}}+\frac{{{{e}^{{6x}}}}}{6}+C.$
B. $4x+\frac{4}{3}{{e}^{{3x}}}+\frac{{{{e}^{{6x}}}}}{6}+C.$
C. $4x+\frac{4}{3}{{e}^{{3x}}}+\frac{{{{e}^{{2x}}}}}{2}+C.$
D. $12{{e}^{{3x}}}+6{{e}^{{6x}}}+C.$