Because it is a parallel circuit, short circuit is not considered (otherwise it will burn out the power supply). When R2 is disconnected, A measures R 1 current, V 1 measurement R 1 voltage, and V2 is 0 (measuring a section of wire). R 1 is broken, both V 1V2 measure R2, and a measures R2, all of which have indicators. Therefore, only R2 has encountered problems in opening the circuit.

Look at the options again, only B is right-