Explanation:

- Touch and go is an idiom that describes a situation that is very uncertain or delicate. It often means the outcome is not clear and could go either way.

- Option 1: Unchanging

- Means something that remains constant or does not change.

- Option 2: Undoubted

- Means something is certain or not questioned.

- Option 3: Unimportant

- Describes something that is trivial or not significant.

- Option 4: Uncertain

- Means not sure or predictable, something with an uncertain outcome.

- Correct Answer: This aligns with the meaning of "touch and go."