A:2H2(g)+ O 2(g) = 2H2O(1)H = —142.9kJ·molˉl
B:2H2(g)+ O 2(g) = 2H2O(1)H = —571.6kJ·molˉl
C:2H2+O2 = 2H2OH = —571.6lkJ·molˉl
D:H2(g)+O 2(g) = H2O(1)H = +285.8kJ·molˉl
It's surprising that your brother Russian so quickly—he hasn't lived there very long.