Explanation:

Let's go through the options and sentences:

- Option 1: Come in

- This usually means to enter or arrive, which doesn't fit any of the contexts.

- Option 2: Come upon

- This typically means to encounter or discover, which is not suitable here.

- Option 3: Come apart

- Correct choice.

- ? This means to break or separate into pieces.

- All sentences reference things that break or separate (a top and bottom coming off, life falling apart, a play unraveling).

- Option 4: Come down

- This means to decrease or descend, which doesn't fit the scenarios.

- Option 5: No improvement required

- It implies that the original phrases were correct, which isn't the case here.

So, the correct answer is Option 3: Come apart.

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