In the circuit shown in figure potential difference between A and B is

10 V

Potential difference is divided among two capacitance C₁ and C₂ in the inverse ratio of their capacities when it is final in series.

Therefore

Voltage across P and Q is

$=190 \times \frac{C}{C+\text {Capacitance across P and Q}}$

equivalent capacitance between P and Q

$=190 \times \frac{C}{C+\frac{15 C}{4}}$ = 40 volt

Potential difference between P and Q (i.e. 40 volt)

Will divide between two capacitor C and 3C which is in series.

Therefore voltage across 3C capacitance.

volt $=40 \times \frac{C}{C+3 C}$ = 10 Volt

Hence (C) is correct choice