Which statement correctly defines capacitance for a two-conductor system?

Why is the electric field between ideal large parallel plates often treated as uniform?

For a spherical Gaussian surface of radius $r$ centered on a point charge $Q$, which expression follows from Gauss's law for the electric field magnitude?

Starting from $C=\frac{Q}{V}$ and $V\left(A\right)-V\left(B\right)=kQ(\frac{1}{A}-\frac{1}{B})$, which expression for the capacitance of concentric spherical shells is correct?

A spherical capacitor is completely filled with a dielectric of relative permittivity $\kappa =4.5$. The inner radius is $1.5\text{ cm}$ and the outer radius is $2.0\text{ cm}$. What is the capacitance?