Answer:
(d) Ammonia
Explanation:
When ammonia is kept at very high pressure and low temperature then its turns into liquid state but nitrogen and hydrogen is in gases state so we can easily find hydrogen as a byproduct from ammonia
Ammonia is considered as one of the primary candidate for the production of hydrogen
[tex]2NH_3\rightarrow 2N_2+3H_2[/tex]
So option (d) will be correct option