Failure to Come to the Rescue of Someone in Serious

Failure to come to the rescue of someone in serious danger is a crime in Canada

A) under all circumstances
B) only when the person in danger communicates his/her plight to you
C) only when there is a pre-existing duty to act, such as a parent failing to come to the rescue of his/her small child
D) only when there is a pre-existing duty to act and an emergency call to officials (like 911) is not available.