If x4 + x2y2 + y4 = 21 and x2 + xy + y2 = 7, then the value of \(\left( {\frac{1}{{{x^2}}}\; + \;\frac{1}{{{y^2}}}} \right)\) is:

• A. 5/2
• B. 7/4
• C. 7/3
• D. 5/4