1. Given data

• Mass of structure: $M = 50 \times 10^3\,\text{kg}$
• Number of identical columns: $4$
• Inner radius of each hollow cylinder: $r = 50\,\text{cm} = 0.5\,\text{m}$
• Outer radius of each hollow cylinder: $R = 100\,\text{cm} = 1.0\,\text{m}$
• Young's modulus of steel: $Y = 2.0 \times 10^{11}\,\text{Pa}$
• Acceleration due to gravity: $g = 9.8\,\text{m/s}^2$

We need the compression strain in each column.

2. Load supported by each column

Since the load is uniformly distributed among 4 identical columns,

$F = \frac{Mg}{4}$

First calculate total weight:

$Mg = 50 \times 10^3 \times 9.8 = 4.9 \times 10^5\,\text{N}$

So force on each column:

$F = \frac{4.9 \times 10^5}{4} = 1.225 \times 10^5\,\text{N}$

3. Cross-sectional area of each hollow column

For a hollow cylinder,

$A = \pi(R^2 - r^2)$

Substitute values:

$A = \pi(1.0^2 - 0.5^2) = \pi(1 - 0.25) = 0.75\pi\,\text{m}^2$

$A \approx 0.75 \times 3.1416 = 2.356\,\text{m}^2$

4. Stress in each column

$\text{Stress} = \frac{F}{A}$

$\text{Stress} = \frac{1.225 \times 10^5}{2.356} \approx 5.20 \times 10^4\,\text{Pa}$

5. Compression strain

Using

$Y = \frac{\text{Stress}}{\text{Strain}}$

So,

$\text{Strain} = \frac{\text{Stress}}{Y} = \frac{5.20 \times 10^4}{2.0 \times 10^{11}}$

$\text{Strain} = 2.60 \times 10^{-7}$

6. Match with options

The calculated compression strain is

$\boxed{2.60 \times 10^{-7}}$

So the correct option is B.

7. Comparison with stored correct answer

Stored correct answer: B

Our derived answer: B

They match.