Correct option is (B) square
Vertices are A(0, 0), B(1, 0), C(1, 1) and D(0, 1).
\(\because\) AB = \(\sqrt{(1-0)^2+(0-0)^2}\) = 1 unit,
BC = \(\sqrt{(1-1)^2+(1-0)^2}\) = 1 unit,
CD = \(\sqrt{(0-1)^2+(1-1)^2}\) = 1 unit,
DA = \(\sqrt{(0-0)^2+(0-1)^2}\) = 1 unit.
Also AC = \(\sqrt{(1-0)^2+(1-0)^2}\) = \(\sqrt2\) unit
BD = \(\sqrt{(0-1)^2+(1-0)^2}\) = \(\sqrt2\) unit
\(\because\) AB = BC = CD = DA and AC = BD
\(\therefore\) ABCD is a square.