Velocity of light = 3 \ imes 10^{10} cm/sec.Velocity of an electron in the orbit is given by the expression, v = \\dfrac {nh}{2\\pi mr} ,where, h is Planck's constant =6.6256 \ imes 10^{-34} Js. m is mass of electron = 9.1096 \ imes 10^{-31} kg. r is radius of orbit = 0.529 \ imes 10^{-10} \ imes n^2 m.For 1^{st} orbit of H-atom, r = 0.529 \ imes 10^{-10} \ imes 1^2 m.Substituting these values in the expression of velocity, we get v = 2.18 \ imes 10^{8} cm/sec.Comparing the velocity of the first orbit of H-atom with the velocity of light, we get to know that velocity of the first orbit of H - atom is \\dfrac{1}{100}th of the velocity of light.Hence, the correct option is 'B'.