Mary Jane Steps onto a Crowded Elevator

Mary Jane steps onto a crowded elevator.Suddenly, she feels something hard being rubbed against her buttocks.She is unable to move away and does not want to reach behind her with her hand.Since she is too modest to say anything, she just stands there and exits the elevator at the very next floor.Mary Jane has just been the victim of:

A) tribadism.
B) troilism.
C) frotteurism.
D) exhibitionism.