Chọn đáp án đúng

A. $\frac{5}{9}+\frac{2}{3}=\frac{5+2}{9+3}=\frac{7}{12}$

B. $\frac{5}{9}+\frac{2}{3}=\frac{5+2}{9x3}=\frac{7}{27}$

C. $\frac{5}{9}+\frac{2}{3}=\frac{5}{9}+\frac{6}{9}=\frac{11}{9}$

D. $\frac{5}{9}+\frac{2}{3}=\frac{5x2}{9x3}=\frac{10}{27}$