A Charged Ring Having Radius $R$ And Total Charge $Q$ Is Lying in the X-Y Plane and Centered at the Is

A charged ring having radius $R$ and total charge $Q$ is lying in the x-y plane and centered at the origin. The expression for the electric field as $z \rightarrow 0$ (in the z direction) is

A) $E _ { z } = 1 / \left( 4 \pi \varepsilon _ { 0 } \right) Q / R ^ { 2 }$
B) $E _ { z } = 1 / \left( 4 \pi \varepsilon _ { 0 } \right) Q / ( z + R ) ^ { 2 }$
C) $E _ { z } = 1 / \left( 4 \pi \varepsilon _ { 0 } \right) Q / ( R - z ) ^ { 2 }$
D) $E _ { z } = 1 / \left( 4 \pi \varepsilon _ { 0 } \right) Q z / R ^ { 3 }$