"a" and "an" are articles, which are adjectives, not prepositions. For some reason, no two or three word prepositions seem to be included in the quiz, such as "in spite of" or "ahead of." These are called compound prepositions.
Agree about "a" and "an" . . . why not "the"? Because they're not prepositions! Quite a few have been added since I was in the sixth grade. Including the French "sans". Why is that the only non-English word included?
No, because in order to use them as prepositions you have to pair them with "of." Like, you can be behind something, or before it, or around it, but you can't be right it. You have to be right OF it, so "of" is the actual preposition.
In 8th grade – which was, alas, a very, very long time ago – we had to memorize "all" of the prepositions. Frighteningly, I still remembered most of them, plus guessed several more… and still only got a 41! So, sorry Miss Holmes; I'm afraid your "complete" list was not so complete!
Many of these are nouns, adjectives, participles, and adverbs rather than prepositions, and I believe there are some prepositions that are not included (unto, for example)
I think you're right that they may be some missing, but I'm pretty sure all of the ones listed are indeed prepositions, at least when used in the correct context.
could "half" be considered a preposition? And are multiple word prepositions not counted as prepositions in English? One of the first prepositions I learnt in English was "in front of" so I was a bit disappointed with it not being accepted here
You can be behind a car (eg), but not ahead a car. It would be ahead of.
And what happened to *unto*?
I suggest you check with a reputable dictionary rather than Wiki