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Practically speaking, it depends on company policy. Available for Sale functions as sort of a catch-all for any securities that the company can’t decide whether they are Trading Securities or Held to Maturity.
From a CFA perspective, if a question did directly ask you this, it usually is made fairly obvious in the passage (e.g. “Jonah Underwood, CFA, is not planning to hold Security A to maturity. He wants the security’s unrealized gains/losses to be reflected in the income statement. What accounting treatment should be used for Security A?”)