Which of the following best describes how the structure of ice benefits the organisms that live in the water below?

The water molecules in ice are considerably far apart as compared to cold water of 4 degrees centigrade and below. This, therefore, makes ice less dense than water at these temperatures (because they are fewer water molecules in ice per unit volume). This is why ice floats on cold water below 4 degrees centigrade. Ice, being a bad conductor of heat, shields the water below an ice sheet from excessive heat loss to the atmosphere. This is why water remains liquid below an ice sheet protecting the marine life below from complete freezing.