If the function $f ( x ) = \left\{ \begin{array} { l } \frac { 2 } { x } \left\{ \sin \left( k _ { 1 } + 1 \right) x + \sin \left( k _ { 2 } - 1 \right) x \right\} , \quad x < 0 \\ 4 , \quad x = 0 \end{array} \quad \right.$ is continuous at $\mathrm { x } = 0$, then $\mathrm { k } _ { 1 } ^ { 2 } + \mathrm { k } _ { 2 } ^ { 2 }$ is equal to\\
(1) 20\\
(2) 5\\
(3) 8\\
(4) 10