Which one of the following statements is correct with respect to basic character?

How can you explain the higher stability of $BCl_3$ as compared to $TlCl_3$?

Account for the following observations:
$(A)$ $AlCl_3$ is a Lewis acid.
$(B)$ Though fluorine is more electronegative than chlorine yet $BF_3$ is a weaker Lewis acid than $BCl_3$.
$(C)$ $PbO_2$ is a stronger oxidizing agent than $SnO_2$.
$(D)$ The $+1$ oxidation state of thallium is more stable than its $+3$ state.

Which of the following represents the correct order of acidic strength?

In the $15^{th}$ group of the periodic table,the elements $N, P, As, Sb$,and $Bi$ are present. As we move from $N$ to $Bi$,how do the oxides with the general formula change?

$P_4 O_{10}$ is the anhydride of