2)In this second paragraph describe for your boss why it is important not to look at these four personnel function in isolation from each other. How is it better for the development of any one of them to involve all four? How is it better for the organization if all of these not only take each other into account, but are better and better to the degree they are well integrated with each other.

The four is describing job Description, Training and Development, Performance Appraisal and Selection System.