Assertion: If the path of a charged particle in a region of uniform electric and magnetic field is not a circle, then its kinetic energy may remain constant.
Reason: In a combined electric and magnetic fields region, a moving charge experiences a net force `F =qE +q(v xx B)`, where symbols have their usual meanings.
Options:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.