Find the missing term in the following problem. \[{{\left( \frac{3x}{4}-\frac{4y}{3} \right)}^{2}}=\frac{9{{x}^{2}}}{16}+\frac{16{{y}^{2}}}{9}+\underline{\,\,\,\,\,\text{?}\,\,\,\,\,}\]

• A.  2xy       
• B.  -2xy   
• C.  12xy   
• D.         -12xy