The Speed of a Particle Moving Along the Curve $\mathbf { r } ( t ) = e ^ { t } \mathbf { i } + \cos ( t ) \mathbf { j } - \sin ( t ) \mathbf { k }$

Multiple Choice

The speed of a particle moving along the curve $\mathbf { r } ( t ) = e ^ { t } \mathbf { i } + \cos ( t ) \mathbf { j } - \sin ( t ) \mathbf { k }$ is

A) $\sqrt { e ^ { 2 t } + 1 }$
B) $\sqrt { 11 }$
C) $\sqrt { 8 t ^ { 2 } + 1 }$
D) $\sqrt { e ^ { 2 t } - 1 }$
E) $\sqrt { 8 t ^ { 2 } - 1 }$