The magnitude of potential energy per unit mass of object at surface of earth is E. then the escape velocity of the object is

$(a)\;\sqrt {2E} \quad (b)\;\sqrt {4E^2} \quad (c)\;\sqrt E \quad (d)\;\sqrt {E/2}$

Potential energy per unit mass $=E$
Total potetial energy $=mE$
Which is equal to binding energy
Hence :
$\frac{1}{2}mv_e^2=mE$
$v_e=\sqrt {2E}$