Our recruitment in Luoyang

When the switch S is closed and the meters A and B are voltmeters, the two resistors are connected in series, then the voltage at both ends of R 1 and the voltage at both ends of R2 = ir2. The index ratio of the two meters is U A: U B = 3: 1.

So u1:UB = 2:1= IR1:IR2 = r1:R2;

When the switch S is turned off and the two ammeters A and B are ammeters, the two resistors are connected in parallel, and I a: I b = UR2: (UR2+UR1) = UR2: (UR2+U2R2) = UR2: (2U2R2+U2R2) = UR2: 3U2R2 = 2: 3.

So choose D.