如图所示电路中,R1=3Ω,R2=6Ω,当开关S1与S2闭合、S3断开时,电流表的示数为0.6A当开关S1与S3闭合、S2断开时,电流表的示数为:[ ]A.0.9A B.2.7A C.1.8A D.0.3A答案:A来源:搜全贸