4. Calculate
$$
\begin{array}{l}
\sqrt{(43 \times 17)^{2}+(43 \times 26)^{2}+(17 \times 26)^{2}} \\
=(\quad) .
\end{array}
$$
(A) 1407
(B) $938 \sqrt{3}$
(C) 1876
(D) $938 \sqrt{2}$
4. A.

Notice that,
$$
\sqrt{(a+b)^{2}\left(a^{2}+b^{2}\right)+a^{2} b^{2}}=a^{2}+a b+b^{2} .
$$