Which is an example of bullying?

a. Karen invites Ben to her party even though she does not think he will be able to come.

b. Olivia and Eddie do not get along so they sit in different areas of the classroom.

c. Every Friday, Susan and Julia tell their classmates to invite everyone to the mall except for Gina.

d. Bradley tells Stan that if Stan disagrees with him while they work on a project, he will tell the teacher.