The correct answers are B and D because making data-driven decisions to determine cloud architectural design and testing systems at production scale are AWS Cloud design principles. Making data-driven decisions to determine cloud architectural design means that users should collect and analyze data from their AWS resources and applications to optimize their performance, availability, security, and cost. Testing systems at production scale means that users should simulate real-world scenarios and load conditions to validate the functionality, reliability, and scalability of their systems. The other options are incorrect because they are not AWS Cloud design principles. Paying for compute resources in advance means that users have to invest heavily in data centers and servers before they know how they will use them. This is not a cloud design principle, but rather a traditional IT model. Emphasizing manual processes to allow for changes means that users have to rely on human intervention and coordination to perform operational tasks and updates. This is not a cloud design principle, but rather a source of inefficiency and error. Refining operational procedures infrequently means that users have to stick to the same methods andpractices without adapting to the changing needs and feedback. This is not a cloud design principle, but rather a hindrance to innovation and improvement. Reference: AWS Well-Architected Framework