Which of the following is NOT correct about hydrides? I. Saline...

Which of the following is NOT correct about hydrides? I. Saline hydrides are stoichiometric and metallic hydrides are non-stoichiometric II. $\mathrm{BeH}_2$ is monomeric whereas $\mathrm{MgH}_2$ is polymeric III. Hydrides of the elements of Group 13 are electron deficient and those of Group15 are electron rich IV. NaH reacts with water and liberates $\mathrm{H}_2$ whereas $\mathrm{B}_2 \mathrm{H}_6$ does not react with water