E field 2!

A disc has charge distribution $\sigma$ and radius R . What is the Electric Field in at a point P , located a distance x directly above the center of the disc?

A: $2\pi { k }_{ e }\sigma (1-\frac { x }{ \sqrt { R^{ 2 }+x^{ 2 } } } )$

B: $2\pi { k }_{ e }\sigma (1-\frac { x }{ ({ { R }^{ 2 }+{ x }^{ 2 }) }^{ \frac { 3 }{ 2 } } } )\\ \\$

C: $2\pi { k }_{ e }\sigma (1-\frac { 2x }{ \sqrt { R^{ 2 }+x^{ 2 } } } )\\ \\$