Which of the following elementary reactions are unimolecular? Select all that apply.
A. N2O4 (g) → 2NO2 (g)
B. PCl5 (g) → PCl3 (g) + Cl2 (g)
C. 2CO (g) + O2 (g) → 2CO2 (g)
D. 2HI (g) → H2 (g) + I2 (g)
E. 2NO (g) → N2O2 (g)