If \({x^2} + \frac{1}{{{x^2}}} = \frac{7}{4}\) for x > 0, then what is the value of \({x^3} + \frac{1}{{{x^3}}}\)?

• A. (3√3)/5
• B. (3√15)/5
• C. (3√15)/8
• D. (3√5)/8