What key stage involves defining your project? a. Representing your data in a trustworthy manner b. Working with data c. Developing your design solution d. Formulating your brief

The correct answer is letter "C": Developing your design solution.

Explanation:

Every project borns with the idea of finding a solution to a problematic situation. While designing a project coming up with what the solution is for the problem that you would like to attempt solving is vital because from there part all the steps on what and how it is going to be done.