While Jessica, Ashley, and Bryan are snowboarding, they ignore warning signs indicating that they have left the marked trail and are entering dangerous territory where they become lost. While climbing the mountain as part of the rescue effort, a snowplow accidentally cuts a nearby town's main electrical cable. Due to the loss of her electric heat, Ethel, an elderly woman, dies of hypothermia. The boarders' negligence in ignoring the warning signs is: a. not the cause of Ethel’s death. b. the proximate cause of Ethel’s death. c. the causation in fact, but not the proximate cause, of Ethel’s death. d. the superseding cause of Ethel’s death.