Question

which one is correct please give explanation​

Answer 1

Answer:

I think option B .... because they are in their standard states...

Answer 2

∆fH is only defined when 1 mol if reactant is formed after getting adequate heat (i.e endothermic).

1 mol of reactant is only formed in C and D.

In option D , the reactant is NO2, it's not a constituent element ... It needs to be prepared first.

So the final correct option is C.