Which of the following is the formation reaction for CaO(s) ?

Question

can you check my answer(the one that has star next to it)
A. Ca(s) + 1/2O2(g)= CaO(s).
B. CaO(s)= Ca(s) + 1/2O2(g)
C. Ca2+(aq) + O2–(aq)= CaO(s)
D. 2 Ca(s) + O2(g)= 2CaO(s) (*)
E. 2 CaO(s)= 2 Ca(s) + O2(g)

Answer 1

Yes, D looks fine. Why is A not correct as the reactants and product are correct and it balances in terms of atoms?

Answer 2

I think A is the correct answer as it gives the heat of formation for one mole. D gives the heat of formation for two moles.

Answer 3

A is probably not correct because the coefficent(1/2) is not a whole number

Answer 4

A is correct for 1mol of CaO