由电路图可知,电阻R1与R2串联,电阻R2两端电压U2=UV2=3V,电阻R1两端电压U1=UV1-UV2=9V-3V=6V,两电阻阻值之比 R1 R2 = U1 I U2 I = U1 U2 = 6V 3V = 2 1 ;故选A.