A small mercury drop is charged such that its surface charge density is 2 $\mathrm{\mu C}/{\mathrm{m}}^2$. Exactly 125 such drops are combined to form a big drop. What is the surface charge density of the big drop?

• A

  2 $\mathrm{\mu C}/{\mathrm{m}}^2$

• B

  (125 x 2) $\mathrm{\mu C}/{\mathrm{m}}^2$

• C

  (5 x 2) $\mathrm{\mu C}/{\mathrm{m}}^2$

• D

  (25 x 2) $\mathrm{\mu C}/{\mathrm{m}}^2$