Bias can be very difficult to overcome. For instance, social networks help people get jobs. While this benefits some, it means that it is harder for those outside the network. Why does this contribute to a lack of diversity in hiring? 

A.
Most workplaces seek to eliminate diversity so this is not a problem anymore.

B.
People naturally have a bias against giving someone a job who they do not know.

C.
People tend to know others who belong to similar social groups, so hiring within networks rarely leads to diversity.

D.
Most people think that diversity only applies to categories like race and religion, so they do not consider other kinds of diversity.