The boarders' negligence in ignoring the warning signs is: the causation in fact, but not the proximate cause, of Ethel's death.
Explanation:
Snowboarding is a game enjoyed during snow fall in winter season. It is recreational activity. A snow board is attached to the feet of the rider and slide in the snow-covered slope. It is important to notice the warning signs while snowboarding. It is a kind of dangerous game, so the instructions should be followed carefully.
In the above scenario, three friends went on for snowboarding. They haven’t notice the warning signs and entered into the dangerous zone. A snowplow accidentally cuts the electrical cable of nearby town, so electrical heat couldn’t be produced in that area. Ethel lost her life due to hypothermia.