The concept of "Splinternet" was mentioned in the Week $9($digital technology and democracy$)$ lecture. How is this concept relevant to the study of global internet usage?

A$.$ It illustrates the declining popularity of the internet globally

B$.$ It shows the unifying effect of the internet across different cultures

C$.$ It underscores the uniformity of internet experiences worldwide

D$.$ It highlights the fragmentation and differing regulations of the internet in various regions