Answer: Al + O2
Step-by-step explanation:
A general classification of reactions uses four general types of reactions.
These are:
1) combination or synthesis
2) substitution or single replacement
3) double replacement
4) decomposition.
Of those the scheme of synthesis type is:
A + B → AB
That is the schem with the given reaction Al + O2:
Al + O2 → Al2O3
Then that is the answer.
F2 + HCl, Ca + H2O, and Li + HCl are under the scheme of single replacement: A + BC → BA + C