Amalgamations. Again

Chemistry Level 1

Aluminium can form an amalgam with mercury. However, when I put drops of liquid mercury on a solid aluminium, no reaction occurs.

Which is the most probable explanation of this situation?

There is a layer of aluminium oxide between the substances Mercury is too volatile so it evaporates before it can react with the aluminium Solid aluminium cannot form amalgamation with mercury There is a layer of mercury oxide between the substances