Correct answer is 1:1
one mole of any substance,compound , or elements contain particles equal to avagadro's number i.e. 6.022
1 mole of NH3 =6.022 molecules of NH3
and
1 mole of HNO3 =6.022 molecules of HNO3
therefore , the ratio of molecules of NH3 and HNO3 is 1:1