Please help this question got me confused. Plants and animals native to the temperate deciduous forest biome do all but what?

1. Hibernate
2. Suffer from humus in soil
3. Cooperate
4. Migrate

Average annual precipitation and are the two major features that define the biomes on earth.

Which of these serves as a reference for comparison during a scientific investigation? a)outcome variable (dependent variable) b) test variable (independent variable) c)control group d)hypothesis

Me with these questions image attached