Which of the Following Shows the Reaction Associated with the Standard

Which of the following shows the reaction associated with the standard heat of formation of a compound?

A) CaO(s) + CO₂(g) $\to$ CaCO₃(s)
B) CO(g) + Cl₂(g) $\to$ COCl₂(g)
C) 4 C(s,graphite) + 4 H₂(g) $\to$ C₄H₈(g)
D) F₂(g) + H₂(g) $\to$ 2 HF(g)
E) Cl₂(g) + 3 F₂(g) $\to$ 2 ClF₃(g)