Explanation:

- Disintegrate (Option 1): This means to fall apart into small pieces or decay. It matches perfectly with the group of words "To fall apart as a result of decay."

Correct Answer

- Dislocate (Option 2): This means to disturb the normal position, usually bone from a joint. It's unrelated to decay.

- Discontinue (Option 3): This means to stop something from continuing. It's not about falling apart or decaying.

- Dishevelled (Option 4): This describes something untidy or messy, usually in appearance. It doesn't pertain to decay.