Bài giải:

$12{{x}^{3}}{{y}^{2}}-\frac{3}{7}{{x}^{4}}{{y}^{2}}+2x{{y}^{3}}-{{x}^{3}}{{y}^{2}}-x{{y}^{3}}+{{x}^{4}}{{y}^{2}}-5$

= $\left( 12{{x}^{3}}{{y}^{2}}-{{x}^{3}}{{y}^{2}} \right)+\left( -\frac{3}{7}{{x}^{4}}{{y}^{2}}+{{x}^{4}}{{y}^{2}} \right)+\left( 2x{{y}^{3}}-x{{y}^{3}} \right)-5$

= $11{{x}^{3}}{{y}^{2}}+\frac{4}{7}{{x}^{4}}{{y}^{2}}+x{{y}^{3}}-5$

Đáp án đúng là: A