The Tangential Component $a _ { \mathrm { T } } ( t )$

Multiple Choice

The tangential component $a _ { \mathrm { T } } ( t )$ of the acceleration of a particle moving along the curve $\mathbf { r } ( t ) = 2 t \mathbf { i } - \sin t \mathbf { j } + \cos t \mathbf { k }$ is

A) $\sqrt { 56 }$
B) $\sqrt { 65 }$
C) 0
D) $\sqrt { 73 }$
E) $\sqrt { 78 }$