Final answer:
A a. NoSQL database is suggested for Donna's requirements because it can handle a variety of data types, facilitate storage on a group of servers, and offers flexible data structures, making it a better fit than a relational database for her scenario.
Step-by-step explanation:
If Donna's requirements include handling a variety of data types, storing data on a group of servers, and needing very flexible data structures, I would suggest a NoSQL database would likely be a better fit than a relational database. NoSQL databases are known for their ability to manage a wide variety of data formats, from structured to semi-structured to unstructured. They also provide great scalability options and are designed to be distributed across several servers easily. This approach would offer more flexibility in data models compared to traditional relational databases, which require a predefined schema and are not as accommodating to diverse data types or rapid changes.
Furthermore, the scalability aspect of NoSQL databases would benefit the flexibility to scale out (horizontal scaling) by adding more servers into the pool as needed, which is generally more complicated in a relational database environment. However, the choice between NoSQL and relational databases also depends on other factors such as the specific business requirements, the consistency needs, and the expertise of the team managing the database.