Answer: D. Cost and time.
Answer analysis: When evaluating the key factors for programmers to choose a project language, we need to consider the association between each option and project success and efficient development.
A. Project requirements: This is one of the most important factors when choosing a programming language. Different programming languages have different characteristics and advantages and are suitable for solving different types of problems. Therefore, understanding the specific needs of the project, including functions, performance, scalability, etc., is the first step in choosing a programming language.
B. Developer skills and experience: Developer skills and experience are also key factors. Choosing a programming language that developers are familiar with and have rich experience with can reduce development difficulty, improve development efficiency, and reduce errors and delays caused by unfamiliar technology.
C. Ecosystem: The ecosystem of a programming language includes community activity, the richness of third-party libraries and tools, etc. A language with an active community and rich third-party libraries can help developers solve problems faster, improve development efficiency, and enjoy the support and resources provided by the community.
D. Cost and time: Although cost and time are very important in project management, they are usually not factors that directly select programming languages. Cost and time are more related to project planning, resource allocation, and schedule management. Of course, some programming languages may indirectly affect the cost and time of a project due to their learning curve, development efficiency, or difficulty in integrating with other technologies, but these factors are not the direct reasons for choosing a programming language.
In summary, the key factors that are not programmers' choice of project language are D, cost, and time. Although these factors are important, they do not directly determine the choice of programming language, but are more related to project management and resource allocation.