A beam of `alpha`-particles passes undeflected through crossed electric and magnetic fields with `E = 6.6 xx 10^6 Nc^-1` and B = 1.2 tesla. The speed of `alpha`-particles is

Options

A. `5 xx 10^6 ms^-1`
B. `5.5 xx 10^6 cm s^-1`
C. `5.5 xx 10^6 ms^-1`
D. `2.5 xx 10^6 ms^-1`.