In Which of the Following Situations Would a Court Be

In which of the following situations would a court be likely to find that the witness to the situation had an affirmative duty to act?

A) Where a pedestrian witnessed an auto accident in which one of the drivers was injured.
B) Where an airline attendant witnessed one passenger threaten another passenger.
C) Where the driver of a car saw a two-year-old toddler wandering in the middle of a busy street.
D) All of these are situations where legally there is an affirmative duty to act.