Correct Answer: Briefly

Solution : The correct option is the first option.

Explanation:
In a nutshell means briefly or concisely summarising something, like putting the essence of it into a nutshell.

The meanings of the other options are as follows:

• Constructively refers to doing something in a way that contributes positively or helps to improve a situation.
• Scrupulously means doing something meticulously or with great attention to detail.
• Knotty describes something complicated or complex, often with difficult problems or issues to solve.

Therefore, the correct option answer is briefly.