Which of the following molecules is theoretically not possible?

The compound in which the number of $d\pi - p\pi$ bonds are equal to those present in $ClO_4^{-}$ is:

Which of the following pairs have the same bond angles?
$(a) BF_3, BCl_3$
$(b) PO_4^{3-}, SO_4^{2-}$
$(c) BF_3, PF_3$
$(d) NO_2^+, N_2O$
$(e) N_3^-, NO_2$
Select the correct option:

Number of $S-S$ bonds in $H_2S_nO_6$ is:

Observe the following structure. The formal charges on the atoms $1, 2, 3$ respectively are:

Which of the following behaves as a Lewis acid?