Which of These Situations Represents Collective Action in Service of Meeting

Which of these situations represents collective action in service of meeting a social norm?

A) Some construction workers decide to work overtime so they will be paid more than their coworkers.
B) Three typists compete to see who can make the fewest errors in a 10-page document.
C) Amish farmers work together to raise a barn in the spirit of cooperation and mutual support.
D) A family of four decides to move from Wyoming to Arkansas.