Which aspect of Service Design is missing from the list below?
1. The design of services
2. The design of service management systems and tools
3. The design of technology architecture and management systems
4. The design of the processes required
5. ?
a) The design of functions
b) The design of Service Level Agreements (SLAs)
c) The design of applications
d) The design of measurement systems, methods and metrics
答案是哪一个，大家一起来分析吧。。。。。

参考3.6 Design aspects

答案：d