4. Let four distinct real numbers $a, b, c, d$ satisfy
$$
\begin{array}{l}
\left(a^{2011}-c^{2011}\right)\left(a^{2011}-d^{2011}\right)=2011, \\
\left(b^{2011}-c^{2011}\right)\left(b^{2011}-d^{2011}\right)=2011 . \\
\text { Then }(a b)^{2011}-(c d)^{2011}=(\quad) .
\end{array}
$$

Then $(a b)^{2011}-(c d)^{2011}=(\quad)$.
(A) -2012
(B) -2011
(C)2012
(D) 2011
4. B.

From $a \neq b$, we know $a^{2011} \neq b^{2011}$.
Thus, $a^{2011}$ and $b^{2011}$ are the two distinct real roots of the quadratic equation in $x$:
$$
\left(x-c^{2011}\right)\left(x-d^{2011}\right)=2011,
$$
which is
$$
x^{2}-\left(c^{2011} \div d^{2011}\right) x+(c d)^{2011}-2011=0.
$$
By Vieta's formulas, we get
$$
\begin{array}{l}
a^{2011} b^{2011}=(c d)^{2011}-2011 . \\
\text { Therefore, }(a b)^{2011}-(c d)^{2011}=-2011 .
\end{array}
$$