A Particle Moves in the Yz-Plane Along the Curve Represented $\mathbf { r } ( t ) = ( 4 \cos t ) \mathbf { j } + ( 9 \sin t ) \mathbf { k }$

Multiple Choice

A particle moves in the yz-plane along the curve represented by the vector-valued function $\mathbf { r } ( t ) = ( 4 \cos t ) \mathbf { j } + ( 9 \sin t ) \mathbf { k }$ . Find the minimum value of $\left\| \mathbf { r } ^ {t } \right\|$

A) 6
B) 4
C) 7
D) 9
E) 8