# A gaseous compound of nitrogen and hydrogen contains $\;12.5\%\;$ (by mass) of hydrogen . The density of the compound relative to hydrogen is 16 . The molecular formula of the compound is :

$(a)\;NH_{2} \qquad(b)\;N_{3}H\qquad(c)\;NH_{3} \qquad(d)\;N_{2}H_{4}$