Five identical capacitor plates are arranged such that they make four capacitors each of 2 $\mu F$. The plates are connected to a source of emf 10 V. The charge on plate C is

Four capacitors are in parallel charge across each $q=CV$. Two surfaces of plate C marks tow capacitors, one with B and other with D and C is connected to positive terminal of the battery. Hence,

$q_c=2CV=+40\mu \mathrm{C}$