Which of the following statements are correct?
(i)$\quad$ Solution culture/hydroponics contains all essential minerals except $\quad$$\quad$one, the usefulness of which is to be determined.
(ii) $\quad$Na, Si, Co and selenium are beneficial element required by $\quad$$\quad$$\quad$$\quad$higher plants.
(iii) $\quad$Zn is the activator of nitrogenases while Mo is the activator of $\quad$$\quad$ $\quad$$\quad$alcohol dehydrogenase.
(iv) $\quad$Zn is needed for auxin synthesis.