What Value of the Constant a Makes the Vector Field $\mathbf { F } ( x , y , z ) = 2 x z \mathbf { i } + a y ^ { 2 } z \mathbf { j } + \left( x ^ { 2 } + y ^ { 3 } \right) \mathbf { k }$

Multiple Choice

What value of the constant a makes the vector field $\mathbf { F } ( x , y , z ) = 2 x z \mathbf { i } + a y ^ { 2 } z \mathbf { j } + \left( x ^ { 2 } + y ^ { 3 } \right) \mathbf { k }$ conservative?

A) $- 2$
B) $- 1$
C) $0$
D) $1$
E) $2$
F) $3$
G) $4$
H) $5$