4. It is known that the three sides of a triangle are the three roots of the equation
$$
x^{3}-9 x^{2}+26 x-24=0
$$

Then this triangle is ( ) triangle.
(A) Right
(B) Obtuse
(C) Acute
(D) Uncertain
4. B.
$$
\begin{array}{l}
\text { Given } x^{3}-9 x^{2}+26 x-24=0 \\
\Rightarrow\left(x^{3}-2 x^{2}\right)-\left(7 x^{2}-14 x\right)+(12 x-24)=0 \\
\Rightarrow(x-2)\left(x^{2}-7 x+12\right)=0 \\
\Rightarrow(x-2)(x-3)(x-4)=0 \\
\Rightarrow x_{1}=2, x_{2}=3, x_{3}=4 .
\end{array}
$$

Therefore, the lengths of the sides of the triangle are $2, 3, 4$.
Since $2^{2}+3^{2}<4^{2}$, the triangle is an obtuse triangle.