Which of the following best completes the following sentence, $$The new standard for social networking sites is to offer tools, widgets, applications, and features that encourage $\_\_\_\_\_\_$; sites provide people with the tools they need to reveal elements of their digital identities.$?$

a$.$

Social lock$-$in$.$

b$.$

Statuscasting.

c$.$

Message internalization.

d$.$

Social sharing.

e$.$

None of these.