Which of the Following Reactions Is the Most Likely to Give

Multiple Choice

Which of the following reactions is the most likely to give off heat?

A) Mg(s) $\rightarrow$ Mg(g)
B) Mg(g) $\rightarrow$ Mg²⁺(g) + 2 e^-
C) MgCl₂(s) $\rightarrow$ Mg²⁺(g) + 2 Cl^-(g)
D) Mg(g) + 2 Cl(g) $\rightarrow$ MgCl₂
E) all these reactions should give off energy