A Confederate Stands near a Participant at a Bus Stop

A confederate stands near a participant at a bus stop and drops some papers. The dependent variable is whether the participant helps the confederate pick them up. In a factorial design, one independent variable is whether the confederate is male or female and the other is whether the confederate has a cane or not. Which of the following describes a potential main effect in this experiment?

A) Participants help the confederate more when he or she has a cane.
B) Participants help the confederate at a fairly high rate.
C) Participants help the male confederate more when he has a cane but they help the female confederate at the same rate regardless of whether she has a cane.
D) Many participants refuse to help.