23. Three numbers are randomly and independently chosen from the closed interval $[0,1]$. Then the probability that these three numbers are the sides of a triangle is ( ).
(A) $\frac{1}{6}$
(B) $\frac{1}{3}$
(C) $\frac{1}{2}$
(D) $\frac{2}{3}$
(E) $\frac{5}{6}$
23. C.

Let $x, y, z \in [0,1]$, and assume $z \geqslant x, y$. Since $x, y, z$ are the sides of a triangle, we know $x+y>z$. By geometric probability, the probability that satisfies the condition is $\frac{1}{2}$.