a
The case of formation and stality of hydrides decreases ravidly from to \(B H_{3}\). This is evident from their theirsociation temperature which decosses for \(N H_{3}\) to \(B H_{3} .\) As we group the size of central from thoreases and thus metal- hydrogen bond becomes weaker due to decreased overlap between the large central atom and small hydrogen atom.

Most stable to least stable order

\(N H_{3}>P H_{3}>A s H_{3}>S b H_{3}>B i H_{3}\)