d
Capacitance of sphere is given by:

\(C=4 \pi \in_{0} r\)

If, \(C=1\, \mathrm{F}\) then radius of sphere needed:

\(r=\frac{C}{4 \pi \epsilon_{0}}=\frac{1}{4 \pi \times 8.85 \times 10^{-12}}\)

or, \(r=\frac{10^{12}}{4 \pi \times 8.85}=9 \times 10^{9}\, \mathrm{m}\)

\(9 \times 10^{9}\, \mathrm{m}\) is very large, it is not possible to obtain such a large sphere. Infact earth has radius \(6.4 \times 10^{6}\, \mathrm{m}\) only and capacitance of earth is \(711\, \mu \mathrm{F}\)