Ge and Si diodes conduct at 0.3 V and 0.7 V respectively, if Ge and Si diode are reverse biased in turn, the value of V0 changes by
0.5 V
0.4 V
0.3 V
0 V
when Ge is conducting V0= 9.7V when Si is working V0= 9.3 v so difference is 0.4 V