Explanation:

- She is asking for trouble:

- Option:3, for

- This is the correct usage. When someone is "asking for trouble," they are behaving in a way that is likely to lead to problems or negative consequences.

- She is asking at trouble:

- Option:1, at

- This is incorrect. "At" does not fit in this context. We don't use "at" when referring to seeking or inviting trouble.

- She is asking in trouble:

- Option:2, in

- This is incorrect. "In" is used for describing being within or inside something, not suitable here.

- She is asking on trouble:

- Option:4, on

- This is incorrect. "On" might be used for time or surfaces, not suitable in this context.