Explanation:

- The idiom "in a nutshell" typically means to summarize something concisely or to explain in a brief manner.

- Option 1: in control - This means having command or authority over a situation. Not related to the idiom.

- Option 2: in short - This means giving a brief summary or explanation.

- This is the correct meaning of "in a nutshell."

- Option 3: in serious trouble - Refers to being in a difficult or problematic situation. Not relevant to the idiom.

- Option 4: in disgrace - Implies being in a state of shame or loss of respect. Does not relate to the idiom.