In which of the following reactions is the position of equilibrium not affected by an increase in pressure?

• A.3Fe_(s) + 4H₂O_(g) ⇌ Fe₃O_4(s) + 4H_2(g)
• B.2NO_2(g) ⇌ N₂O _4(g)
• C.3H_2(g) + N_2(g) ⇌ 2NH_3(g)
• D.2SO_2(g) + O_2(g) ⇌ 2SO_3(g)