Statement I : Bond angle in ${\mathrm{NH}}_3> {\mathrm{PH}}_3>{\mathrm{AsH}}_3> {\mathrm{SbH}}_3$

Statement II : ${\mathrm{PH}}_3$ is thermally more stable than ${\mathrm{NH}}_3$ 

Down the group in the hydrides of ${15}^{\mathrm{th}}$ group as the electronegativity of central atom decreases, bond angle decreases.

Down the group affinity of hydrogen with central atom decreases. X-H bond enthalpy decreases,thermal stability decreases.