Explanation:

- The group of words is "that which cannot be satisfied."

- Option 1: Insatiable

- This correctly means incapable of being satisfied or quenched.

- Example: An insatiable appetite for knowledge.

- This is the correct answer.

- Option 2: Impossible

- Means not able to occur or be done.

- Example: It's impossible to predict the future with certainty.

- Option 3: Improbable

- Refers to something that is unlikely to occur.

- Example: It is improbable that it will snow in the desert.

- Option 4: Incredible

- Means something that is difficult to believe or astonishing.

- Example: The magician's tricks were incredible.