If P is the vertical relation and ρ is the vertical deflection, then the modulus of sub-grade reaction is _______

• A. \(k_s=\frac{P}{ρ}\)
• B. \(k_s=\frac{1}{P}\)
• C. \(k_s=\frac{ρ}{P}\)
• D. \(k_s=\frac{P}{2ρ}\)