Pipes are made of the element Lead so the answer should be d) lead pipe
The chemical equation for this reaction is this:
CO2 + 4H2 = CH4 + 2H2O
from the equation, the mole ration of CO2 to CH4 is ratio 1:1
and CH4 = 25.1
The mole ratio of H2 to H2O is 4:2
therefore, mole of H2 = 19.1* 4/2 = 38.2
The moles of methane produced is 38.2 moles