3. $a, b, c$ are real numbers, and $a^{2}-b c-8 a+7=0$, $b^{2}+c^{2}+b c-6 a+6=0$. Then the range of values for $a$ is ( ).
(A) $-\infty1$.
(C) $1<a<13$.
(D) $1 \leqslant a \leqslant 9$.
\begin{tabular}{c}
3 \\
\hline $\mathrm{D}$
\end{tabular}