The system described by the following governing equation of motion, will have how many natural frequencies?\(\left[ {\begin{array}{*{20}{c}} m&0\\ 0&m \end{array}} \right]\left[ {\begin{array}{*{20}{c}} {\mathop x_1 }\\ {\mathop x_ 2} \end{array}} \right] + \left[ {\begin{array}{*{20}{c}} {2k}&{ - k}\\ { - k}&{3k} \end{array}} \right] + \left[ {\begin{array}{*{20}{c}} {{x_1}}\\ {{x_2}} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} 0\\ 0 \end{array}} \right]\)

• A. 4
• B. 3
• C. 2
• D. 1