Consider the following statements regarding streamline(s) :

i) It is a continuous line such that the tangent at any point on it shows the velocity vector at that point

ii) There is no flow across streamlines

iii)  \(\frac{{{\rm{dx}}}}{{\rm{u}}} = \frac{{{\rm{dy}}}}{{\rm{v}}} = \frac{{{\rm{dz}}}}{{\rm{w}}}\) is the differential equation of a streamline, where u, v and w are velocities in directions x, y and z, respectively

iv) In an unsteady flow, the path of a particle is a streamline

Which one of the following combinations of the statements is true?