A:若a表是电流表,b表是电压表,则电阻R1、R2并联
B:若a表是电流表,b表是电压表,则电阻R1、R2串联
C:若a表是电压表,b表是电流表,则电阻R1、R2并联
D:若a表是电压表,b表是电流表,则电阻R1、R2串联
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