3. The equation $9 x^{2}+4 y^{2}-12 x-4 y+3=0$ has ( ) integer solutions.
(A) : None
(B) Some
(C) Too many
(D) Exactly one integer solution
3. (A).

The original equation is transformed into $(3 x-2)^{2}+(2 y-1)^{2}=2$. Therefore, the system can be:
$$
\begin{array}{l}
\left\{\begin{array} { l } 
{ 3 x - 2 = 1 , } \\
{ 2 y - 1 = 1 ; }
\end{array} \quad \left\{\begin{array}{l}
3 x-2=-1, \\
2 y-1=-1 ;
\end{array}\right.\right. \\
\left\{\begin{array} { l } 
{ 3 x - 2 = 1 , } \\
{ 2 y - 1 = - 1 ; }
\end{array} \left\{\begin{array}{l}
3 x-2=-1, \\
2 y-1=1 .
\end{array}\right.\right.
\end{array}
$$

Among these, two sets have real solutions $\left\{\begin{array}{l}x=1, \\ y=1\end{array}\right.$ and $\left\{\begin{array}{l}x=1, \\ y=0 .\end{array}\right.$