The Vector R(t) Is the Position Vector of a Particle

Multiple Choice

The vector r(t) is the position vector of a particle at time t. Find the angle between the velocity and the acceleration vectors at time t = 0.
- $$\mathbf { r } ( \mathrm { t } ) = \sin ^ { - 1 } ( 7 \mathrm { t } ) \mathbf { i } + \ln \left( 8 \mathrm { t } ^ { 2 } + 1 \right) \mathbf { j } + \sqrt { 7 \mathrm { t } ^ { 2 } + 1 } \mathbf { k }$$

A) $\frac { \pi } { 4 }$
B) $\frac { \pi } { 3 }$
C) $\frac { \pi } { 2 }$
D) 0