$\lim _ { x \rightarrow 0 } \frac { \left( e ^ { x } - 1 \right) \tan ^ { 2 } x } { x ^ { 3 } }$\\ (a) does not exist\\ (b) exists and equals 0\\ (c) exists and equals $\frac { 2 } { 3 }$\\ (d) exists and equals 1.