Choose the past perfect or the past simple. 4. I went to the library, then I (buy) some milk and went home.

{ "answer": "4. I went to the library, then I **bought** some milk and went home.

**Explanation:**
* The sentence describes a sequence of actions in the past. 'Went' is in the past simple. 'Buy' is happening in the past and is part of a sequence of actions, so it should be in the past simple ('bought')." }