Answer would be A. Why because isolation means that nothing can move in or out
P1V1/T1=P2V2/T2 P2=1/2 P1 V1=1 T1=298K
1 P1/298= (1/2) P1V2/373 cross P1
1/298=1/2V2/373
1/298=1/V2 746
v2=746/298
V2=2.5L
Total number of atoms = 7
Total number of H atom = 5
% of H in ammonium hydroxide = 5/7 ×100 = 71.4 %