Which project is the most suitable for an agile development model, such as scrum?
A. a project that is difficult but has strict, well-documented requirements
B. a simple project that should take no more than 3 months to complete because the team has done a similar project in the past
C. a project that is based on an existing design document and uses off-the-shelf components
D. a project that lacks well-defined requirements and is of some significant complexity