Young's modulus from stress and strain Steps:

• Force per rod: 10 kN total / 4 rods = 2.5 kN = 2500 N.
• Stress: 2500 N / (250 × 10^{-6} m²) = 10^7 N/m².
• Strain: ΔL / L = 0.10 × 10^{-3} m / 2.0 m = 5 × 10^{-5}.
• E = stress / strain = 10^7 / 5 × 10^{-5} = 2.0 × 10^{11} N/m² (option A). Why A is correct:
• Matches the definition E = stress / strain in Hooke's law, yielding standard steel value of 200 GPa. Why the others are wrong:
• B: Underestimates by factor of 10, likely from incorrect area conversion (e.g., mm² to m² error).
• C: Incorrect combination, perhaps halving stress while adjusting strain wrongly.
• D: Overestimates by factor of 4, from applying total 10 kN force to one rod instead of per rod.

Final answer: A