Which of the following is used as Green solvent?

What is vapour density of $\mathrm{O}_2$ gas?

Identify the correct statement regarding geometry and lone pair of electrons present in $\mathrm{CH}_4$ and $\mathrm{SiCl}_4$.

What type of hybridisation is present in square planar geometry of complex $\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$