What part is the most important in maintaining cell homeostasis

This is a really subjective or iffy question, because there are so many technicalities. But I know that you would likely be taught a specific way and told certain things in high school biology. That being said the answer they are likely looking for is the following. The most important organelle in cellular homeostasis is the cell membrane or phospholipid bilayer. And assuming the answer is the cell membrane it would be because constant flow of substances, in and out of the cell, via the many forms of transport whether active, passive, or facilitated is required for and/or results in cellular homeostasis.

i believe it's c. the trait for large beaks will be passed on to future generations through natural selection.

since eventually smaller beaks would have to find another source of food or even eventually just die out from the lack of food.