There is not much to be added - both answers are either wrong or make no sense.
For a mixture to be called an alloy it has to contain at least one metal. No metal, no alloy. Questions doesn't mention this condition, so the "alloy" answer is incorrect, as there are plenty of two elements mixtures that are not alloys.
Answering "another name for mobile electrons" with "mobile electron" is incorrect, as it is not "another name", it is the same name. It is not even a trick question, it is plain wrong.