question_answer

If \[f(x)=\left| \begin{matrix}    \cos (x+\alpha ) & \cos (x+\beta ) & \cos (x+\gamma )  \\    \sin (x+\alpha ) & \sin (x+\beta ) & \sin (x+\gamma )  \\    \sin (\beta -\gamma ) & \sin (\gamma -\alpha ) & \sin (\alpha -\beta )  \\ \end{matrix} \right|\] and \[f(0)=-2\] then \[\sum\limits_{r=1}^{30}{\left| f(r) \right|}\] equals

A)  2                                

B)  30

C)  60                  

D)  120