Which of the following series of emission spectral lines for hydrogen observed in visible region?

What is the number of faraday required to produce 0.18 g aluminium at cathode during electrolysis of molten $\mathrm{AlCl}_3$ ? (Molar mass of $\mathrm{Al}=27 \mathrm{~g} \mathrm{~mol}^{-1}$ )

Which pair of metal ions from following have same number of unpaired electrons?

Which from following compounds contains oxygen as a heteroatom?