Which of the following molecules is theoretically not possible?

Observe the following species:
$(i)$ $NH_3$
$(ii)$ $AlCl_3$
$(iii)$ $SnCl_4$
$(iv)$ $CO_2$
$(v)$ $Ag^{+}$
$(vi)$ $HSO_4^{-}$
How many of the above species act as Lewis acids?

The number of bonds between sulphur and oxygen atoms in $S_{2}O_{8}^{2-}$ and the number of bonds between sulphur and sulphur atoms in rhombic sulphur,respectively,are

Identify the incorrectly matched set from the following:

$Me_3B$,$BH_3$,and $BF_3$ are three Lewis acids. Which one of the following is the correct sequence of these acids in order of their increasing acid strength?

Which of the following orders is incorrect $:-$