The structure of orthophosphoric acid is

Phosphorus pentachloride in the solid state exists as:

Explain why $NH_3$ is basic while $BiH_3$ is only feebly basic.

Which of the following dissolves in hot conc. $NaOH$ solution?

Which of the following statements about phosphine $(PH_3)$ is/are correct?
$(a)$ It has a rotten egg-like smell.
$(b)$ In aqueous solution and in the presence of light,it yields red phosphorus and hydrogen.
$(c)$ It explodes with $Br_2$.
$(d)$ In its pure form,it is non-inflammable.

Regarding the hydrides of group $15$ elements $EH_{3}$ $(E = N, P, As, Sb, Bi)$, select the correct statement from the following:
$A$. The stability of hydrides decreases down the group.
$B$. The basicity of hydrides decreases down the group.
$C$. The reducing character increases down the group.
$D$. The boiling point increases down the group.
Choose the correct answer from the options given below: