As a result of short growing seasons, people in extremely cold regions often eat a lot of
a. fiber
b. protein
c. vegetables
d. fresh fruits

The correct answer is option b. "protein".

Explanation:

People living in extremely cold regions have to adapt to short growing seasons and to the lack of fresh fruits and vegetables for most of the year. As a result northern people often eat a lot of protein from animal sources. The most extreme example of this situation is the Eskimo's diet, which for 10 months of the year live almost entirely from hunting fish, birds, caribou, seals and other animals.

allowed for the prediction of the properties of missing elements.

well for one plants are always the producer, so a is the answer. a wolf is more of the consumer(predator) and the deer is the prey so i know those two are out of the question. also mushrooms are fungi/fungus so a is the producer.