An electric line of force in the $xy$ plane is given by equation $x^2+y^2=1$. A particle with unit positive charge, initially at rest at the point $x = 1, y = 0$ in the $xy$ plane

Question

$\begin {array} {1 1} (a)\;\text{ not move at all} \\ (b)\;\text{ will move along straight line} \\ (c)\;\text{will move along the circular line of force} \\ (d)\;\text{information is insufficient to draw any conclusion} \end {array}$