Bài giải:

${{\left( \frac{2}{3}xy \right)}^{2}}.{{y}^{2}}-\frac{2}{5}{{x}^{2}}{{\left( y.y \right)}^{2}}+\left( \frac{2}{3}x{{y}^{3}} \right)xy-\frac{1}{4}{{x}^{2}}{{y}^{4}}$

= $\frac{4}{9}{{x}^{2}}{{y}^{4}}-\frac{2}{5}{{x}^{2}}{{y}^{4}}+\frac{2}{3}{{x}^{2}}{{y}^{4}}-\frac{1}{4}{{x}^{2}}{{y}^{4}}$

= $\left( \frac{4}{9}-\frac{2}{5}+\frac{2}{3}-\frac{1}{4} \right){{x}^{2}}{{y}^{4}}$

= $\frac{83}{180}{{x}^{2}}{{y}^{4}}$

Đáp án đúng là: B