Virtual strain is ____________

• A. ε(ф)=\(\frac{dx}{d\phi}\)
• B. ε(ф)=\(\frac{d\phi}{dx}\)
• C. ε(ф)=\(\frac{dx}{d\varepsilon}\)
• D. ф(ε)=\(\frac{d\varepsilon}{d\phi}\)