The correct option is C Value of ε1 will be ε
∵ Reading in Ammeter is zero, so the current (i) will only flow in the upper circuit. Where I=ε1R+r
=ir=iR,
∴ (b) is correct.
Here, vQ−vR=ε1−rir=ε1−r.ε1R+r=ε1RR+r=ε
∵ no current is flowing through 2R
ε1=ε(R+r)R
∴ (a) is correct and (c) is incorrect
∵ no current is flowing through 2R
∴ potential difference across 2R = 0
∴ (d) is also correct.