Learn Arabic (Modern Standard): أأجبت عن السؤال أم نسيت؟ - Did you answer the question or did you forget?

In Arabic, أم is specifically used in alternative questions that ask you to choose between two options (like "A or B?"). It is almost always paired with the question particle أ at the start of the sentence. If you were making a regular statement instead of a question, you would use أو.

Why are there two alifs at the beginning of أأجبت?

The very first أ is the question particle (used here to mean "did...?"). The second أ is simply the first letter of the past tense verb أجبت (you answered). Because they are written together, they sit side-by-side as أأجبت.

Why is the preposition عن used after the verb "answer"? In English, we just say "answer the question".

Arabic verbs often pair with specific prepositions that don't match English. The verb for "to answer" (أجاب) generally requires the preposition عن (about/from) before the thing being answered. So literally, you are saying "Did you answer about the question?".

How do we know نسيت means "did you forget" when there is no question word right before it?

The question particle أ at the very beginning of the sentence turns the whole sentence into a question. Because the word أم (or) links the two verbs together, the "did you" question format automatically carries over from the first verb to the second one.