Statement I : Ammonia is highly soluble in water, solubility of other hydrides of 15th group is very less.

Statement II : Ammonia can form H-bonds with water ,  other hydrides of 15th group cannot involve in H-bonding

Covalent compounds like ${\mathrm{NH}}_3, \mathrm{HF}$, lower alcohols , lower carboxylic acids, ${\mathrm{H}}_2{\mathrm{O}}_2$ are capable of forming intermolecular H-bonding with water.

Thus they all are soluble in water.

${\mathrm{PH}}_3,{\mathrm{AsH}}_3,{\mathrm{SbH}}_3 \mathrm{and} {\mathrm{BiH}}_3$ cannot form H-bonds with water because

X-H bond in them is less polar due to large size and lesser electronegativity of the central atom;