Learn Swedish: Myndigheten hade redan erhållit brevet, men ingen besvarade det. - The authority had already received the letter, but nobody replied to it.

The root verb is hålla, which means to hold or to keep. When you add the inseparable prefix er-, it creates the verb erhålla, meaning to receive or to obtain. The prefix er- usually indicates acquiring or achieving something, though it belongs to a very formal register.

Could I use fått instead of erhållit in this sentence?

Yes, fått (the supine form of få, meaning to get or receive) is perfectly correct and much more common in everyday speech. However, erhålla is highly formal and bureaucratic, making it the most natural choice here since we are talking about myndigheten (the authority).

What is the grammatical difference between besvarade det and svarade på det?

The root verb svara (to answer) is intransitive, meaning it requires the preposition på to connect to an object. Adding the inseparable prefix be- creates the transitive verb besvara. Transitive verbs take a direct object without a preposition. So besvarade det means the same thing but is more concise and fits the formal tone of the sentence.

Just as a refresher, why does the adverb redan go right after hade?