Let Then $\int$ C $\mathbf { F } \bullet d \mathbf { r }$

Multiple Choice

Let $\mathbf { F } ( x , y , z ) = z \mathbf { i } + x \mathbf { j } + y \mathbf { k } , \mathbf { r } ( t ) = \cos t \mathbf { i } + \sin t \mathbf { j } + t \mathbf { k } , 0 \leq t \leq 2 \pi$ . Then $\int$ C $\mathbf { F } \bullet d \mathbf { r }$ is

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