Which of the following exhibits the highest solubility in water?

The strongest acid among the given options is:

In the following reaction,identify the nature of the products formed by the complete hydrolysis of $\underline{P}_4O_8$ at $R.T$:
$\underline{P}_4O_8 + H_2O \longrightarrow H_3PO_3 + H_3PO_4$

The electronegativity of a group $13$ element '$E$' is the same as that of $Ge$ (on the Pauling scale and up to one decimal point). The $CORRECT$ statements about $E^{3+}$ are:
$A$. It can act as a reducing agent.
$B$. It can act as an oxidizing agent.
$C$. $E^{3+}$ is more stable than $E^+$.
$D$. The standard electrode potential value for $E^{3+}/E$ is positive.

What happens when excess water is added to a solution of $BiCl_3$?

Given below are two statements:
Statement $I$: Like nitrogen that can form ammonia,arsenic can form arsine.
Statement $II$: Antimony cannot form antimony pentoxide.
In the light of the above statements,choose the most appropriate answer from the options given below: