Explanation:

Resistance of upper \(\operatorname{arm}=2\, \Omega+2\, \Omega=4\, \Omega)\) is in parallel with the diagonal resistance \((2\, \Omega)\) and the resistance of lower arm ( \(=2\, \Omega+2\, \Omega=4\, \Omega\) ).
\(\therefore \quad\) The equivalent resistance between \(A\) and \(B\) is
\(\frac{1}{{{R_{eq}}}} = \frac{1}{{4\,\Omega }} + \frac{1}{{2\,\Omega }} + \frac{1}{{4\,\Omega }} \Rightarrow {R_{eq}} = \frac{{4\,\Omega }}{4} = 1\,\Omega \)