A block of mass ‘m’ is connected to two springs of stiffness K1 and K2 as shown in the figure. f1 and f2 are the frequencies of the block when connected to K1 and K2 independently. Then the frequency of ‘m’ when connected to K1 and K2 as in the figure is

• A. f = f1 + f2
• B. \(f = f_1^2 + f_2^2\)
• C. \(f = \sqrt {f_1^2 + f_2^2}\)
• D. \(f = \sqrt {f_1^2 - f_2^2} \)