An Australian woman was sent to life in prison for poisoning her husband's family with ___.

The woman was sentenced to life in prison for poisoning her husband's family with mushrooms, specifically toxic wild mushrooms. This case underscores the dangers associated with foraging and consuming wild fungi, which can often be misidentified. The incident received significant media attention, particularly because of the gruesome nature of the crime and the challenge of proving intent and the source of the poison.

In contrast, while rat poison and cyanide are widely known toxic substances associated with poisoning cases, they were not the substances used in this particular crime. Chocolate, although it can be toxic to some animals, is not generally lethal to humans in the quantities that would be harmful in a deliberate poisoning case. Thus, mushrooms are the correct answer as they directly correlate with the specific circumstances of this tragic event.