To find the volume of water that can be stored in a hemisphere with a given radius, we use the formula for the volume of a hemisphere:

\[
V = \frac{2}{3} \pi r^3
\]

where \( r \) is the radius of the hemisphere.

Given:
- Radius \( r = 10.5 \, \text{dm} \)

1. Calculate the volume in cubic decimeters (dm³):

\[
V = \frac{2}{3} \pi (10.5)^3
\]

\[
(10.5)^3 = 1157.625
\]

\[
V = \frac{2}{3} \times \pi \times 1157.625
\]

\[
V = \frac{2}{3} \times 3.1416 \times 1157.625
\]

\[
V = 2 \times 3.1416 \times 385.875
\]

\[
V = 2425.5 \, \text{dm}^3
\]

2. Convert the volume from cubic decimeters to liters:

Since \( 1 \, \text{dm}^3 = 1 \, \text{liter} \),

\[
V = 2425.5 \, \text{liters}
\]

The correct answer is:

B. 2425.5 liters