$29 \cdot 37 x^{4}+2 x^{2}+9$ has a factor of
(A) $x^{2}+3$.
(B) $x+1$.
(C) $x^{2}-3$.
(D) $x^{2}-2 x-3$.
(E) None of the above.
(6th American High School Mathematics Examination, 1955)
[Solution] From $x^{4}+2 x^{2}+9=x^{4}+6 x^{2}+9-4 x^{2}$
$$
\begin{array}{l}
=\left(x^{2}+3\right)^{2}-4 x^{2} \\
=\left(x^{2}+2 x+3\right)\left(x^{2}-2 x+3\right) .
\end{array}
$$

Therefore, the answer is $(E)$.