Among the following species,identify the isostructural pairs: $NF_3,NO_3^-,BF_3,H_3O^+,HN_3$

$\begin{array}{1 1}(a)\;[HN_3,NO_3^-]\;and\;[BF_3,H_3O^+]\\(b)\;[NF_3,HN_3]\;and\;[NO_3^-,BF_3]\\(c)\;[NF_3,H_3O^+]\;and\;[NO_3^-,BF_3]\\(d)\;[NF_3,H_3O^+]\;and\;[HN_3,BF_3]\end{array}$

$NF_3,H_3O^+,BF_3,NO_3^-$ are trigonal planar.
$N_3H\rightarrow$ linear shape.
Hence (c) is the correct answer.