A physical quantity of the dimensions of length that can be formed out of c, G and e24πε0 is [c is velocity of light, G is universal constant of gravitation and e is charge.

As, force, F=e24πε0r2⇒e24πε0=r2⋅FPutting dimensions of rand F, we get⇒       e24πε0=ML3T−2                                              …(i)Also, force, F=Gm2r2⇒[G]=M−1L3T−2                     …(ii)and            1c2=1L2T−2=L−2T2                           …(iii)Now, checking optionwise                                =1c2Ge24πε01/2=L−2T2L6T−41/2=[L]