Question

http://prntscr.com/uiuv3y
Explain the answer please!
Thanks!

Answer 1

Picture from: https://prnt.sc/uiuv3y.

As we know, two points connected with an ideal wire are equipotential. Than means that $V_1 = V_2$, therefore there is no voltage drop on the resistors between points 1 and 2. So current flows through the (ideal) wire, not trough the resistors. Thus, the resistance of the circuit section between 1 and 2 is zero.

The same is true for circuit section between 3 and 4, its resistance is zero as well.

So, total resistance of circuit between A and B is $0+R+0 = R$.

Answer: $R.$