To determine how long it takes Rosa to decorate 1 cookie, we can start by calculating her rate of decorating cookies.
Rosa can decorate 6 cookies in 24 minutes. Therefore, the time it takes to decorate one cookie can be calculated as follows:
\[ \text{Time per cookie} = \frac{\text{Total time}}{\text{Number of cookies}} = \frac{24 \text{ minutes}}{6 \text{ cookies}} = 4 \text{ minutes per cookie} \]
Thus, the time it takes her to decorate 1 cookie is 4 minutes.
The correct answer is:
C. 4 minutes