The correct option is A 18 μC
Voltage across two parallel elements are equal.
Hence,
Voltage across 4 μF=9 V.
Applying K.V.L in loop containing battery of voltage (ϵ)=12 V, we can find voltage across 6μF capacitor.
So, the voltage across 6μF capacitor will be 12−9=3 V
Therefore, charge (Q)=C×V
=6×3=18 μC