In what way can it be proved that $PH_3$ is basic in nature?

Question

$\begin{array}{1 1} \text{(a)$PH_3 + NaOH \rightarrow PH_3OH + Na$} \\ \text{(b)$PH_3 + HI \rightarrow H_3PO_4+I$} \\ \text{(c) $PH_3 + HI \rightarrow PH_4I$} \\ \text{(d) $PH_3 + H_2O \rightarrow PH_3OH$}\end{array} $