5. In the square in Figure 1, 10000 points are randomly thrown. The estimated number of points that fall into the shaded area (the equation of curve $C$ is $x^{2}-y=0$) is ( ).
(A) 5000
(B) 6667
(C) 7500
(D) 7854
5. B.

According to the problem, the area of the blank region is
$$
\int_{0}^{1} x^{2} \mathrm{~d} x=\left.\frac{1}{3} x^{3}\right|_{0} ^{1}=\frac{1}{3} \text {. }
$$

Therefore, the area of the shaded part is $\frac{2}{3}$, and the ratio of the area of the shaded part to the blank part is $2: 1$.
Thus, the number of points falling into the shaded part is
$$
10000 \times \frac{2}{3} \approx 6667 \text {. }
$$