Answer: Life span, Life expectancy.
Explanation:
Option C Habitat.... Polar bears are only found in the Arctic. The most important habitats for polar bears are the edges of pack ice where currents and wind interact, forming a continually melting and refreezing matrix of ice patches and leads (open spaces in the ocean between sea ice).
Active transport moves molecules across the plasma membrane of a cell with the help of transport proteins and energy (ATP).
Active transport is the means of transport of molecules across the plasma membrane with the help of energy. This method is usually used for the transport of molecule against their concentration gradient, i.e., from lower concentration to higher concentration.
Plasma membrane is the outer layer surrounding the cell. It is made up of lipid bilayer, proteins, carbohydrates and cholesterol. The lipid bilayer is amphipathic since the lipid head is hydrophilic and its tail is hydrophobic. The plasma membrane is semi-permeable in nature.
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Trophic levels go by,
Producer (The nuts)
Primary Consumer (Squirrels)
Secondary Consumer (Raccoons)
Tertiary Consumer (Bear)
So squirrels would be at a lower trophic level.
Hope his help :)