When Is Failure to Come to the Rescue of Someone

When is failure to come to the rescue of someone in serious danger a crime in Canada?

A) under any circumstance
B) only when the person in danger communicates his/her plight
C) only when there is a pre-existing legal 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